Mechanical Properties

These tests may be carried out on freshly applied or aged coatings and are often used to assess test panels after durability or corrosion testing.

Abrasion ResistanceBS 3900-E14, ISO 7784-1
Abrasion ResistanceBS 3900-E15, ISO 7784-2
Abrasion ResistanceASTM D4060
Adhesion TestingBS EN ISO 2409, BS 3900-E6
Adhesion TestingBS EN 24624, ISO 4624
Application Properties and Appearance 
Assessment of BlisteringBS 3900-H2, ISO 4628/2
Assessment of ChalkingBS 3900-H6, ISO 4628/6
Assessment of CrackingBS 3900-H4, ISO 4628/4
Assessment of FlakingBS 3900-H5, ISO 4628/5
Assessment of RustingBS 3900-H3, ISO 4628/3
Chip ResistanceBS AU 148 Part 15
Cupping ResistanceBS EN ISO 1520, BS 3900-E4
Determination of Surface Drying TimeBS 3900-C2, ISO 1517
Determination of Through Drying Time BS 3900-C3, ISO 9117, BS EN 29117
Determination of Recoatability 
Determination of Film ThicknessBS EN ISO 2808, BS 3900-C5
Flexibility TestingBS EN ISO 1519, BS 3900-E1
Flexibility TestingBS EN ISO 6860, BS 3900-E11
Flexibility TestingASTM D 522
Hardness TestingBS EN ISO 1518, BS 3900-E2
Hardness TestingBS EN ISO 1522, BS 3900-E5
Hardness TestingBS EN ISO 2815, BS 3900-E9
Hardness TestingBS 3900-E17, ISO 12137- 1
Hardness TestingBS 3900-E19, ISO 15184
Hardness TestingASTM D 3363
Impact ResistanceBS 3900-E3
Impact ResistanceBS 3900-E7
Impact ResistanceBS EN ISO 6272, BS 3900-E13
Impact ResistanceASTM D 2794
Determination of MFFTASTM D 2354
Determination of Water Vapour PermeabilityASTM D 1653
Determination of Resistance to LiquidsBS EN ISO 2812-1
Determination of Resistance to LiquidsBS EN ISO 2812-2
Determination of Resistance to LiquidsBS EN ISO 2812-3
Determination of Resistance to LiquidsBS EN ISO 2812-4
Scrub Resistance and CleanabilityBS EN ISO 11998
Scrub Resistance and CleanabilityDIN 53778: Part 2
Scrub Resistance and CleanabilityASTM D 2486
Surface Energy and Contact Angle Measurements on Solids 
Determination of Tensile PropertiesASTM D 2370
Wet AdhesionASTM D 6900

The BS and ASTM standards mentioned here are copyright-protected documents and we are not able to provide you with copies. If required however, you can easily obtain copies from the British Standards Institution or the American Society for Testing and Materials.

 

 

Abrasion Resistance: BS 3900-E14 : ISO 7784-1

Scope and Field of Application

BS 3900-E14 and ISO 7784-1 are alternative names for the same method which is intended for determining the resistance to abrasion of a dry film of paint, varnish or related product using abrasive paper attached to a rotating wheel.

There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

Summary of Method

We only use this method to calibrate the equipment. It is essentially the same as BS 3900-E15: ISO 7784-2.

Sample Requirements

Three test panels 100 x 100 x not more than 5 mm

6.3 mm diameter circular central hole.

perfectly flat with a non-textured test surface

weight less than 200 grams

We can cut larger panels to size for you or, if you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

Accreditation

PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

Top of pagePlease contact the Testing Laboratory for further details

Abrasion Resistance: BS 3900-E15, ISO 7784-2

Scope and Field of Application

BS 3900-E15 and ISO 7784-2 are alternative names for the same method which is intended for determining the resistance to abrasion of a dry film of paint, varnish or related product using rotating abrasive rubber wheel.

There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

Summary of Method

The dried film is abraded, under specified conditions, with abrasive rubber wheels which are attached to an abrasion testing machine known as a Taber abraser. The wheels are loaded with specified weights and the test is run for a specified number of cycles. The resistance to abrasion is defined as either:-

  • The loss in mass after a specified number of abrasion cycles.
  • The number of cycles requires to abrade down to an underlying coating or to the substrate
  • This method includes a calibration procedure based on the weight loss obtained when a defined abrasive paper is used to abrade standard zinc panels.

    When requesting this test to be carried you need to specify the type of abrasive wheel to be used, the wheel loading and the number of cycles. The following wheels are available:-

  • Coating Type to be Tested Type of Wheel
  • Coatings of all types including those resistant to general handling CS 10
  • Floor coatings resistant to pedestrian traffic CS 17
  • Floor coatings resistant to vehicle traffic H 22
  • In our experience the most common request is for 500 and 1000 cycles using CS 10 wheels with a 1000 gram load. Under these conditions you can expect a good epoxy floor coating to lose no more than 60 mg after 500 cycles and no more than 120 mg after 1000 cycles.

    Sample Requirements

    Three test panels 100 x 100 x not more than 5 mm

    6.3 mm diameter circular central hole.

    perfectly flat with a non-textured test surface

    weight less than 200 grams

    We can cut larger panels to size for you or, if you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Abrasion Resistance: ASTM D4060

    Scope and Field of Application

    ASTM D4060 is similar to BS 3900-E15/ ISO 7784-2 and the differences between the methods is summarised below.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    The Taber abraser is also used for this method. It is operated in the same way and the resistance to abrasion is expressed as defined above. The main differences between the methods are the way in which the results are expressed, The ASTM method defines resistance to abrasion in three ways:-

  • The wear index which is 1000 times the mass loss in milligrams per cycle.
  • The loss in mass after a specified number of abrasion cycles.
  • The wear cycle per mil which is the number of cycles requires to wear a film through to the substrate per thousandth of an inch of film thickness.
  • The ASTM method includes information on the precision of the measurements both within and between laboratories and sets limits for acceptable variation.

    Sample Requirements

    At least two test panels 100 x 100 x not more than 5 mm

    6.3 mm diameter circular central hole.

    perfectly flat with a non-textured test surface

    weight less than 200 grams

    We can cut larger panels to size for you or, if you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Adhesion Testing: BS EN ISO 2409, BS 3900-E6

    Scope and Field of Application

    BS EN ISO 2409 and BS 3900-E6 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to separation from a substrate when a right-angle lattice pattern is cut into the coating and penetrates through to the substrate.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    This standard defines how a lattice pattern (consisting of two sets of six cuts with the sets at a right angle to each other) should be cut through the film. This reduces the paint film within the lattice to 25 small squares of coating. The standard defines the spacing of the cuts and hence the size of the squares. This varies according to the thickness of the coating.

    A piece of transparent adhesive tape of defined adhesion strength is then applied over the lattice and pulled off. The standard includes a six-point pictorial scale ranging from no coating removed to more than 65% of the squares wholly or partially removed.

    The advantages of the method are:-

  • It is a simple, low cost method.
  • It can be used on test samples where there is only a limited area of flat surface available.
  • It can be used on-site and in situations where it is not practicable to use a tensile test method.
  • The disadvantages of the method are:-

  • It cannot be used on coatings that are more than 250 microns thick or those which have a textured surface.
  • It is not a sufficiently severe test. Unless there are significant adhesion problems, most coating-substrate combinations will show little or no coating detachment.
  • Sample Requirements

    The test can be carried out using a single 150 x 100 mm coated test panel. We can normally carry out the test on coated objects provided they have at least three flat regions at least 40 x 40 mm. The coating must be non textured and less than 250 microns thick.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Adhesion Testing:BS EN 24624: ISO 4624

    Scope and Field of Application

    BS EN 24624 and ISO 4624 and are alternative names for the same method which is used to assess coating adhesion by measuring the magnitude of a perpendicularly applied tensile force needed to detach or rupture the coating. It supersedes BS 3900: E10 which has been withdrawn.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    A suitable adhesive (two-pack epoxy, two-pack polyester or cyanoacrylate) is used to fix a test cylinder to the surface of the coating. Once the adhesive has cured, a blade is used to cut around the circumference of the cylinder and down to the substrate. A tensile testing tool is then fixed to the test cylinder and used to apply a gradually increasing force of up to 100 Kg per square centimetre. The force being applied at that point when the test cylinder detaches from the test piece is noted.

    The advantages of the method are:-

  • It gives you a quantified measure of adhesion
  • It can be used on moderately rough and textured surfaces
  • The fracture surfaces on the disc and substrate can be examined visually and by a number of analytical techniques in order to determine the mode of failure.
  • It is applicable over a wide range of adhesion strengths.
  • The disadvantages of the method are:-

  • You need at least 150 square centimetres of flat surface for each test.
  • The substrate needs to be rigid and be capable of sustaining the applied force without fracturing.
  • There is always the worry that the adhesive modifies the coating and affects the reading obtained.
  • There are some coatings for which we are unable to find a good adhesive.
  • We can use the technique on site but the time needed for the adhesive to cure makes it inconvenient especially in cold/wet environments
  • In our experience a reading of between 20 and 40 kg per square centimetre corresponds to acceptable adhesion. We class anything above 40 kg per square centimetre as good. We have not been able to find an adhesive which can sustain a force of greater than 200 kg per square centimetre so this is the effective upper limit of the test. The following conversion factors may be useful:-

  • To convert kg per square centimetre to pounds per square inch, multiply by 14.2
  • To convert kg per square centimetre to kilopascals or to kilonewtons per square metre, multiply by 98.
  • To convert megapascals to pounds per square inch, multiply by 145.
  • In practice if the coating system has very good adhesion you tend to get cohesive failure of the coating and, in some circumstances, of the substrate.

    Sample Requirements

    We need at least three flat panels for each coating. They should be 150 x 100 x at least 3 mm. Steel or aluminium are the preferred substrates although we have used this test on coatings applied to rigid plastics. Unless the adhesion of the coating is poor, substrate like wood and masonry are liable to undergo cohesive failure first.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Application Properties and Appearance

    Scope and Field of Application

    This is a test designed to measure how easy it is to apply coatings to a substrate using a brush and / or a roller. After application, the appearance and hiding power of the film assessed and the coverage calculated.

    This work is not carried out to any international standard: we use our own in-house method.

    Summary of Method

    This test is suitable for assessing many different types of coatings including interior paints for walls and ceilings, exterior masonry paints, interior and exterior paints for joinery, interior and exterior paints for metal and interior wood stains as well as shed and fence coatings.

    The test is carried out using a substrate appropriate to the type of coating being applied these can be plasterboard, joinery hardboard, steel or Softwood and in the case of wood planed or rough-sawn finished.

    Interior Paints for Walls and Ceilings Plasterboard 1,200 x 1,200 Sealed with thinned white matt emulsion paint. A 200 mm wide black stripe is painted centrally across the board using matt black emulsion. A 200 mm wide black stripe is painted centrally across the substrate.

    An experienced painter applies the coating to the chosen substrate using a brush and / or a roller. The application is carried out gravimetrically according to the general principles of BS 3900-A16 / ISO 7254 (see Determination of Spreading Rate on our page: Testing Paints Before Application). This enables the spreading rate to be calculated.

    The ease of application, if carried out by brush, is rated by the painter according the Ease of Brush Loading and the Ease of Application.

    If coatings are applied using a roller ease of application is rated according to the Ease of Roller Loading, Ease of Application, The Degree of Foaming and Amount of Spatter

    Once the paint has dried, the appearance of the painted substrate is assessed on:

  • Quality of Finish in the case of a Poor finish the rating includes the reason why the coating is rated so (e.g. patchy appearance, runs, streaks etc)
  • Hiding Power All except non-opaque wood coatings and coatings for metal and sheds and fences.
  • Gloss / Sheen All except matt finishes and shed and fence coatings.
  • Sample Requirements

    We require 1 litre of coating.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Top of pagePlease contact the Testing Laboratory for further details

    Assessment of Blistering: BS 3900-H2, ISO 4628/2

    Scope and Field of Application

    BS 3900-H2 and ISO 4628/2 are alternative names for the same method. It is one of a series of methods of designating the quantity and size of common types of defects in paint coatings. Other methods in this series deal with the assessment of chalking, cracking, flaking and rusting.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    It is important to emphasise that the standard describes a method of assessing blistering. It is not a method for testing the resistance of a coating to blistering. If you need to test for resistance to blistering, then please refer to our corrosion testing and durability testing pages and in particular to humidity testing. We will of course be pleased to advise on the most appropriate test for your samples.

    The standard is basically a collection of photographs of test panels showing blisters that vary in both size and density. The photographs are rated for both size and density using four-point scale ranging small/few to large/dense blisters. The sample is compared with these photographs and given the rating of the photographs that bear the closest resemblance.

    Sample Requirements

    This assessment is normally carried out using test panels that have been subject to some form of corrosion or durability testing and the panel size and number will have been selected for that purpose. Basically all we need is a representative test piece with an area for assessment of at least 100 x 100 mm.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Assessment of Chalking: BS 3900-H6, ISO 4628/6

    Scope and Field of Application

    BS 3900-H6 and ISO 4628/6 are alternative names for the same method. It is one of a series of methods of designating the quantity and size of common types of defects in paint coatings. Other methods in this series deal with the assessment of blistering, cracking, flaking and rusting.

    Chalking is defined as the formation of a powdery deposit on the surface of a coating that has been exposed to some form of degradation. It is commonly found on coatings that have been exposed outdoors to sun and rain. The powder is in fact the pigment and extender that remains after the binder has been destroyed by weathering.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    It is important to emphasise that the standard describes a method of assessing chalking. It is not a method for testing the resistance of a coating to chalking. If you need to test for resistance to chalking, then please refer to our durability testing page. We will of course be pleased to advise on the most appropriate test for your samples.

    A length of adhesive tape is applied to the surface of the coating and then removed. Any loosely bound chalk will adhere to the tape and the quantity present is assessed by viewing the tape against a contrasting background and comparing it with a set of five photographs which are included in the standard. The sample is given the rating of the photograph that bear the closest resemblance.

    Sample Requirements

    This assessment is normally carried out using test panels that have been subject to some form of durability testing and the panel size and number will have been selected for that purpose. Basically all we need is a representative test piece with an area for assessment of at least 100 x 100 mm.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Assessment of Cracking: BS 3900-H4, ISO 4628/4

    Scope and Field of Application

    BS 3900-H4 and ISO 4628/4 are alternative names for the same method. It is one of a series of methods of designating the quantity and size of common types of defects in paint coatings. Other methods in this series deal with the assessment of blistering, chalking, flaking and rusting.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    It is important to emphasise that the standard describes a method of assessing cracking. It is not a method for testing the resistance of a coating to cracking. If you need to test for resistance to cracking before weathering, then please refer to flexibility testing (BS EN ISO 1519, BS EN ISO 6860 and ASTM D 522). If you wish to assess the effect of weathering on flexibility, you should visit our durability testing page. We will of course be pleased to advise on the most appropriate test for your samples.

    The standard is basically a collection of drawings of cracked surfaces showing both linear and random cracking that vary in density. The sample is compared with these drawings and given the rating of the drawing that bears the closest resemblance.

    The standard also includes a table which enables you to rate the size of the cracks on a six-point scale ranging from no cracks visible under x 10 magnification to ones that are more than 1 mm wide.

    Sample Requirements

    This assessment is normally carried out using test panels that have been subject to some form of durability testing and the panel size and number will have been selected for that purpose. Basically all we need is a representative test piece with an area for assessment of at least 100 x 100 mm.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Assessment of Flaking: BS 3900-H5, ISO 4628/5

    Scope and Field of Application

    BS 3900-H5 and ISO 4628/5 are alternative names for the same method. It is one of a series of methods of designating the quantity and size of common types defects in paint coatings. Other methods in this series deal with the assessment of blistering, chalking, cracking and rusting.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    It is important to emphasise that the standard describes a method of assessing flaking. It is not a method for testing the resistance of a coating to flaking. If you need to test for resistance to flaking before weathering, then please refer to adhesion testing (BS EN ISO 2409 and ISO 4624). If you wish to assess the effect of weathering on flaking, you should visit our durability page. We will of course be pleased to advise on the most appropriate test for your samples.

    The standard is basically a collection of drawings of flaked surfaces showing both linear and random flaking that vary in size and density. The sample is compared with these drawings and given the rating of the drawing that bear the closest resemblance.

    The standard also includes a tables which enables you to rate the size of the flaked area on a six-point scale ranging from no flakes visible under x 10 magnification to ones that are larger than 30 mm.

    Sample Requirements

    This assessment is normally carried out using test panels that have been subject to some form of durability testing and the panel size and number will have been selected for that purpose. Basically all we need is a representative test piece with an area for assessment of at least 100 x 100 mm.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Assessment of Rusting: BS 3900-H3, ISO 4628/3

    Scope and Field of Application

    BS 3900-H3 and ISO 4628/3 are alternative names for the same method. It is one of a series of methods of designating the quantity and size of common types defects in paint coatings. Other methods in this series deal with the assessment of blistering, chalking, cracking and flaking.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    It is important to emphasise that the standard describes a method of assessing rusting. It is not a method for testing the resistance of a coating to corrosion. If you need to test for resistance to corrosion, please refer to our corrosion testing page. We will of course be pleased to advise on the most appropriate test for your samples.

    The standard is basically a collection of photographs of coated steel surfaces with different degrees of rusting. The sample is compared with these photographs and given the rating of the one that bears the closest resemblance.

    Sample Requirements

    This assessment is normally carried out using test panels that have been subject to some form of corrosion testing and the panel size and number will have been selected for that purpose. Basically all we need is a representative test piece with an area for assessment of at least 100 x 100 mm.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Chip Resistance: BS AU 148 Part 15

    Scope and Field of Application

    BS AU 148: Part 15 is a method of providing information regarding the resistance of a paint system to chipping by the impact of gravel and grit thrown up from road surfaces. We use it to test automotive finishes.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    The test involves dropping 100 quarter-inch diameter hexagonal metal nuts down a 4.5 metre long vertically-mounted tube onto a test panel. The standard includes a set of 6 drawings showing gradations of damage to a paint surface ranging from very slight to very severe. The test panel is compared with these drawings and given the rating of the drawing that resembles it most closely.

    Sample Requirements

    We require 3 coated panels (150 x 100 mm) on an appropriate substrate.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Cupping Resistance: BS EN ISO 1520, BS 3900-E4

    Scope and Field of Application

    BS EN ISO 1520 and BS 3900-E4 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to cracking and/or detachment from a metal substrate when subjected to gradual deformation by indentation under standard conditions. It is a particularly appropriate method for testing pre-coated metal which will be bent or extruded in some factory production process.

    When choosing a test method, you may also wish to consider the mandrel bend tests (BS EN ISO 1519, BS EN ISO 6860 and ASTM D 522). Cupping is potentially a more severe test than the mandrel bend test. In the cupping test, deformation of the panel can be taken to the point where the metal fractures. This does not normally happen during mandrel tests.

    The cupping and mandrel tests are all carried out on coatings applied to flexible metallic substrates. If you are interested in the flexibility or other tensile properties of coatings on different substrates, you may wish to consider tensile testing.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    A coated metal panel is sandwiched between a hemispherical die and a hemispherical indenter. Pressure is applied to the indenter so as to form a dome shape in the panel with the coating on the convex side. The pressure is increased either to a specified depth or until the coating cracks and/or disbonds from the substrate.

    There are a number of ways of examining the coating after test. We recommend using normal corrected vision but you can specify x 10 magnification if you wish.

    Sample Requirements

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    However if you wish to supply us with coated panels it is important that the thickness and composition of the substrate is such that it can be deformed and the substrate itself does not crack under test.

    In practice this means that the steel or aluminium panels must be not less than 0.3 mm and not more than 1.25 mm thick. We require three panels for each coating each of which should be 100 x 150 mm.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Surface Drying Time: BS 3900-C2, ISO 1517

    Scope and Field of Application

    BS 3900-C2 and ISO 1517 are alternative names for the same method which is intended for the determination of the surface drying characteristics of a paint or varnish film which dries by reaction with air or by a chemical reaction of its components.

    This method gives a measure of the time that elapses between the application of a coating and that moment when the surface first becomes sufficiently dry that material no longer adheres to it.

    At this time the sub-surface coating will still be soft and a separate test is required to determine how long it takes for the coating to dry completely. Please refer to the through drying test page for details of the method.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    The coating is applied to a number of test panels which are then left to dry under defined temperature and humidity conditions.

    At suitable intervals, one of the panels is selected and a quantity of small glass spheres (known as Ballotini) are poured onto the surface. A small brush is used in an attempt to remove the spheres from the surface. If they cannot be removed the panels are left to dry for a further period and then the whole process is repeated using a fresh panel.

    The time at which the painted surface is just dry enough for all the spheres to be removed is taken as the surface-dry time.

    This method can also be used as a pass/fail test for surface-dry after a defined time period.

    Our experience of this test is that, at 20°C and 50% relative humidity, solvent borne decorative gloss paints generally surface dry within four hours while decorative matt emulsion paints take about 30 minutes.

    Sample Requirements

    We require 250 ml of sample together with information regarding the film thickness at which the coating should be applied.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Through Drying Time : BS 3900-C3, ISO 9117, BS EN 29117

    Scope and Field of Application

    BS 3900-C3 , ISO 9117 and BS EN 29117 are alternative names for the same method which is intended for the determination of the through drying characteristics of a paint or varnish film which dries by reaction with air or by a chemical reaction of its components.

    This method gives a measure of the time that elapses between the application of a coating and that moment when not only the surface but the entire thickness of the film is dry. We normally supplement this method with an in-house determination of recoatability.

    A separate test is required to determine how long it takes for the surface alone to dry completely. Please refer to the surface drying test for details of the method.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    The coating is applied to a number of test panels which are then left to dry under defined temperature and humidity conditions.

    At suitable intervals, one of the panels is selected and tested using a machine which presses a gauze fabric covered plunger against the film and then rotates it through 90 degrees. If the film is not through-dry, this process will cause visible marring of the surface.

    If the surface of the coating is damaged or marked, the panels are left to dry for a further period and then the whole process is repeated using a fresh panel.

    The time at which the painted surface is just dry enough to remain unmarked during the test is taken as the through-dry time.

    This method can also be used as a pass/fail test for through-dry after a defined time period.

    Our experience of this test is that, at 20°C and 50% relative humidity, solvent borne decorative gloss paints generally through-dry within eight hours while decorative matt emulsion paints take about 45 minutes.

    Sample Requirements

    We require 250 ml of sample together with information regarding the film thickness at which the coating should be applied.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Recoatability

    Scope and Field of Application

    Often customers want to know if a coating can be over coated once it is through dry we assess this by using a our method for recoatability, frequently this test is carried out in combination with the determination of through drying time.

    This work is not carried out to any international standard: we use our own in-house method.

    Summary of Method

    We carry out a determination of recoatablility as soon as the through-dry stage is reached. This involves the application of the coating, by brush, to the newly through-dried film. Any drag on the brush or rivelling of the film when dry is noted.

    Sample Requirements

    We require 250 ml of sample together with information regarding the film thickness at which the coating should be applied.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Film Thickness: BS EN ISO 2808, BS 3900-C5

    Scope and Field of Application

    BS EN ISO 2808 and BS 3900-C5 are alternative names for a number of methods that are applicable to the measurement of the thickness of both wet and dry organic coatings. None of the methods are suitable for measuring metallic coatings but some can be adapted for the measurement of detached organic films. The standard also defines a number of terms concerning the determination of film thickness.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Methods

    Film thickness methods which appear in the standard and which we can carry out, fall into two main categories wet and dry. Wet methods include; Wet Comb Gauge, Wet Wheel Gauge and a Wet Gravimetric Method. These wet methods have the advantage that they are quick and easy to carry out, the disadvantage is that they are not very accurate.

    Dry methods can be very accurate in determining film thickness under laboratory conditions and include; Dry Gravimetric Method, Micrometer, Microscope used in the form of a Paint Inspection Gauge (PIG), Magnetic Induction Meter or Eddy Current Meter. Some of these methods are necessarily destructive or have specific substrate requirements. We will be pleased to advise on the most appropriate method to use with your samples.

    It is important to realise however that there are some samples for which it is impossible to obtain a realistic measure of the film thickness. Examples include highly textured coatings, coatings on uneven substrates and coating applied to substrates that are porous.

    Sample Requirements

    Detached paint flakes should be at least as large as your thumb nail and should include all layers from the one adjacent to the substrate up to the top coat. Our requirements when dealing with coated substrates vary depending on the method to be used and we will be pleased to discuss this with you.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

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    Flexibility Testing: BS EN ISO 1519, BS 3900-E1

    Scope and Field of Application

    BS EN ISO 1519 and BS 3900-E1 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to cracking and/or detachment from a flexible substrate when bent around a cylindrical mandrel.

    When choosing a flexibility test method, you may also wish to consider the cupping test. Cupping is potentially a more severe test than the mandrel bend test. In the cupping test, deformation of the panel can be taken to the point where the metal fractures. This does not normally happen during mandrel tests.

    The cupping and mandrel tests are all carried out on coatings applied to flexible substrates. If you are interested in the flexibility or other tensile properties of coatings on different substrates, you may wish to consider tensile testing.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    This method involves the use of a set of manually operated hinges each of which incorporates a cylindrical rod (known as a mandrel) around which the coated test panel is bent. A total of 12 mandrel diameters are specified ranging from 2 to 32 mm. This method has the option of using the 2 mm mandrel the smallest specified in the standards. This provides a more severe test than the 3.2 mm minimum diameter of the conical mandrel.

    After bending, the coating is examined for cracking and/or detachment using either normal corrected vision or (by agreement) a lens with x 10 magnification.

    Sample Requirements

    We need coated panels with dimensions 100 x 40 x no more than 0.3 mm . The substrate may be steel, tin-plate or soft aluminium. If we are to determine the largest mandrel that causes failure, we need 15 panels for each coating. If you specify the mandrel diameter, we need 3 panels

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

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    Flexibility Testing: BS EN ISO 6860, BS 3900-E11

    Scope and Field of Application

    BS EN ISO 6860 and BS 3900-E11 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to cracking and/or detachment from a flexible substrate when bent around a conical mandrel.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    This method involves the use of a manually operated tool which enables a test panel to be bent around a truncated cone (known as a mandrel). The diameter of the mandrel ranges from 3.2 to 38 mm.

    Before bending, the coating is cut through at 20 mm intervals: these incisions are intended to limit crack propagation. After bending, the coating is examined for cracking and/or detachment using either normal corrected vision or (by agreement) a lens with x 10 magnification. The length of any cracks formed is noted.

    This method has a number of advantages:

    • It is possible to use thicker panels.
    • You can use standard 150 x 100 mm panels.
    • You only use one mandrel which means that you need fewer panels.

    Sample Requirements

    We need 3 coated panels for each coating. The dimensions should be 150 x 100 x no more than 0.8 mm . The substrate may be burnished steel, burnished tin-plate or soft aluminium.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Flexibility Testing: ASTM D 522

    Scope and Field of Application

    ASTM D 522 is a method of determining the resistance to cracking of organic coatings on sheet metal or rubber-type substrates.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    This method describes the use of both conical and cylindrical mandrels.

    The conical mandrel method uses the same equipment as BS EN ISO 6860: BS 3900-E11. The method of determination differs however in that the ASTM method allows for a slow bend time to measure elongation. The measurement of cracking calls for a faster bend time than the BS method and does not include the option of cutting through the coating to limit crack propagation. The ASTM cracking test is therefore somewhat more severe than the BS method.

    The cylindrical mandrel method uses different equipment to that specified in BS EN ISO 1519: BS 3900-E1. The ASTM equipment consists of a series of cylindrical metal mandrels mounted in a frame. The operator selects a mandrel and bends the test panel around it manually. The frame contains 5 mandrels ranging in size from 3.2 to 25 mm. Elongation and cracking tests can be carried out using the same bend times as for the ASTM conical mandrel.

    The ASTM method allows for fewer mandrels which cover a more restricted size range than those specified in the BS EN ISO 1519: BS 3900-E1 method. It could also be argued that the BS hinged tools allow for more controlled and reproducible bending than is possible using the ASTM equipment.

    Sample Requirements

    In order to carry out the conical mandrel test, we need 3 coated panels for each coating. The dimensions for crack testing should be 150 x 100 mm. The substrate may be any sheet metal up to 0.8 mm thick or any rubber-type material up to 13 mm thick. If elongation testing is requires the substrate must be cold-rolled steel 150 x 100 x less than 0.8 mm.

    The requirements for testing using the cylindrical mandrel are the same as the conical mandrel in terms of dimensions. If we are to determine the largest mandrel that causes failure, we need 15 panels for each coating. If you specify the mandrel diameter, we need 2 panels.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Hardness Testing: BS EN ISO 1518, BS 3900-E2

    In some cases the test method will be specified but in others it is necessary to choose the most appropriate method. If you want a coating to be hard because it is going to be used on a floor subject to heavy traffic or on woodwork in a school room then you should consider if testing for resistance to abrasion or impact would be more appropriate.

    Scope and Field of Application

    BS EN ISO 1518 and BS 3900-E2 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to penetration by scratching with a needle.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    This test is capable of good reproducibility however, a flat test panel is required and the values obtained are dependent on the adhesion of coating to substrate.

    The equipment used for this test consists of a horizontal motorised stage on which a coated panel is mounted. A weighted needle rests on the coated surface and forms part of an electric circuit which includes a meter. This meter deflects if the needle penetrates the coating and comes into contact with the metallic substrate.

    During the test the coated panel is driven under the needle and the meter is observed in order to see if the coating is penetrated through to the substrate. After the test, any scratch formed on the coating is examined visually in order to assess the extent and nature of the damage.

    The equipment can be used to determine the minimum load on the needle that will cause penetration through to the substrate. Alternatively it can be used to establish whether a specified needle loading will cause penetration.

    Sample Requirements

    Three test panels of dimensions 125 x 100 x not greater than 1 mm. Substrate must be metal. Coating must be non-conductive, smooth and more than 30 microns thick.

    If you wish, we can prepare the test panels. The quantity of liquid paint we need depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Hardness Testing: BS EN ISO 1522, BS 3900-E5

    Scope and Field of Application

    BS EN ISO 1522 and BS 3900-E5 are alternative names for the same method which is used to assess the hardness of a dry film of paint, varnish or related product by measuring how it reduces the oscillation amplitude of a pendulum.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    This method is the best at obtaining a value, reported in units of time, that depends on hardness alone is capable of good reproducibility and has the advantage of being non-destructive. The test requires a flat test panel.

    There are two types of apparatus defined in this standard The Konig pendulum and The Persoz pendulum. Both pendulums have spherical balls which rest on the coating under test and form the fulcrum. Both employ the same principle i.e. the softer the coating the more the pendulum oscillations are damped and the shorter the time needed for the amplitude of oscillation to be reduced by a specified amount. The two pendulums differ in shape, mass and oscillation time and there is no general relationship between the results obtained using the two pieces of equipment.

    The test simply involves noting the time in seconds for the amplitude of swing to decrease from either 6 to 3 degrees (Konig pendulum) or 12 to 4 degrees (Persoz pendulum)

    Sample Requirements

    Two panels of size 100 x 100 x 5 mm. The substrate should be metal or glass and must be flat and rigid. Coating must be smooth and more than 30 microns thick.

    If you wish, we can prepare the test panels. The quantity of liquid paint we need depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Hardness Testing: BS EN ISO 2815, BS 3900-E9

    Scope and Field of Application

    BS EN ISO 2815 and BS 3900-E9 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to indentation by a weighted metal wheel.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    This test is non-destructive, simple and rapid to carry out. However, many coatings are sufficiently plastic to render the indentation transient and dark-coloured coatings can often make viewing the indentation difficult. Hardness is reported in units of reciprocal length and the test requires a flat test panel.

    The apparatus used in this test is known as the Buchholz indenter. It consists of a sharp edged wheel (made of hardened tool steel) which is mounted in a rectangular block of metal fitted with two feet. When this apparatus rests on a horizontal surface, the effective load on the indenter is 500 grams.

    The test involves placing the indenter on the coating and leaving it for 30 seconds. A x 20 magnification microscope fitted with an eyepiece graticule in then used, together with a light source, to measure the length in mm of the shadow cast by the indentation. The value obtained when 100 is divided by this length is known as the Buchholz Indentation Resistance of the coating

    Sample Requirements

    Two samples 150 x 100 x not less than 1mm. Substrate should be metal or glass and must be flat and rigid. The minimum coating thickness ranges from 15 microns for the hardest coatings to 35 microns for the softest.

    If you wish, we can prepare the test panels. The quantity of liquid paint we need depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Hardness Testing: BS 3900-E17, ISO 12137- 1

    Scope and Field of Application

    BS 3900-E17 and ISO 12137-1 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to marring by a looped or a ring-shaped stylus.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    This test gives a practical measure of the effect of hardness (i.e. resistance to marring) and is good method for assessing the tendency of a coating to be scratched by finger nails, car wash brushes etc. The method requires a flat test panel and values obtained are dependent on the adhesion of coating to substrate.

    The apparatus and the test method are virtually identical to those used in BS EN ISO 1518: BS 3900-E2. The main difference is in the nature of the stylus used. Whereas BS EN ISO 1518: BS 3900-E2 requires the use of a needle-shaped stylus, BS 3900-E17: ISO 12137-1 defines both a loop-shaped and a ring-shaped stylus, either of which can be used.

    Sample Requirements

    Three panels 125 x 100 x not greater than 1 mm. The substrate and the coating thickness should be representative of the intended use of the coating.

    If you wish, we can prepare the test panels. The quantity of liquid paint we need depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Hardness Testing: BS 3900-E19, ISO 15184

    Scope and Field of Application

    BS 3900-E19 and ISO 15184 are alternative names for the same method which is used to assess the hardness of organic coatings using a series of pencils with leads of known hardness.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    In this method hardness is compared with that of familiar items; pencils. The method is simple and rapid to carry out and can easily be carried out on site. The samples can be small and need not be flat unless the use of a pencil holder is desired. Results can be operator dependent and the hardness of pencil leads is not well defined and not always well controlled

    Artists' pencils are made with leads that range in hardness from 9H (very hard) to 9B (very soft). The test equipment consists of a set of 20 pencils together with a holder which allows a pencil to be held at a 45 degree angle while being pushed firmly across the surface of the coating under test. The use of the holder is optional.

    The test procedure starts with the hardest pencil and continues using progressively softer pencils until the hardest pencil that does not scratch, rupture or permanently indent the surface of the coating has been established. This is termed the "Pencil Hardness" of the coating.

    In addition the standard also allows for the determination of "Gouge Hardness" as defined in ASTM D 3363.

    One limitation of this method is the lack of any international standard relating the hardness of pencil leads to any reference scale (e.g the Mohr scale of hardness).

    Our understanding is that there are international variations in hardness. A Japanese HB pencil, for example, is softer than a European HB pencil which in turn is softer than a USA HB pencil.

    There is no standard method for measuring the hardness of pencils. Such methods that do exist rely on a skilled and experienced operative assessing the feel of the pencil when used as a drawing instrument and the blackness of the mark it produces.

    Not all manufacturers produce pencils with consistent and reproducible hardness. Those that do usually have a retained set of pencils, dating back many years, with which current products are compared. The hardness of pencils can vary with time and is likely to be affected by the temperature at which they are stored.

    BS 3900-E19: ISO 15184 lists manufacturers of pencils that have been found suitable for test use. In order to maximise the chances of different laboratories obtaining the same result when testing the same sample we would suggest that they use the same make and the same batch of pencils.

    Sample Requirements

    If the pencil holder is required then we require two test panels measuring 150 x 100 x any thickness and any material provided the substrate is flat and rigid. Coating must be smooth and more than 30 microns thick.

    If you wish, we can prepare the test panels. The quantity of liquid paint we need depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

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    Hardness Testing: ASTM D 3363

    Scope and Field of Application

    ASTM D 3363 is a method which is similar to BS 3900-E19 : ISO 15184.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    In this method hardness is compared with that of familiar items; pencils. The method is simple and rapid to carry out and can easily be carried out on site. The samples can be small and need not be flat. However, results can be operator dependent and the hardness of pencil leads is not well defined and not always well controlled

    This is a similar method to BS 3900-E19: ISO 15184. The main differences between the two methods are that ASTM D 3363 only defines 14 pencils ranging in hardness from 6B to 6H and does not allow for the use of a pencil holder.

    The standard defines "Scratch Hardness" as the hardest pencil that will not rupture or scratch the film ( this is essentially equivalent to "Pencil Hardness" as defined in BS 3900-E19: ISO 15184). The definition of "Gouge Hardness" is the hardest pencil that will not make a cut into the film which is at least 3 mm in length.

    The same limitation regarding BS 3900-E19: ISO 15184 apply here also

    Sample Requirements

    The test piece can be as small as 10 x 10 on any smooth rigid substrate.

    If you wish, we can prepare the test panels. The quantity of liquid paint we need depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Top of pagePlease contact the Testing Laboratory for further details

    Impact Resistance: BS 3900-E3

    Scope and Field of Application

    BS 3900-E3 is a method used to assess the resistance to the impact of a falling weight of a single coat film or multicoated systems of paint, varnish or related products. Although this standard has been superceded by BS EN ISO 6272: BS 3900-E13, we find it is still requested by those who are following old specifications or who wish to correlate the results with data obtained previously.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    The equipment used for this test can be likened to a small guillotine where the blade has been replaced by an indenter which weighs 4.75 Kg. and which is fitted with a 14 mm diameter hemispherical tip. This falls 570 mm to strike a coated test panel which is sandwiched between two die blocks each of which have 18 mm diameter central holes. The indenter is constructed so that its stroke can be lengthened. In the non-lengthened position the indenter passes through the hole in the upper die block and just touches the test panel before stopping.

    The standard does not give any advice regarding by how much the indenter should be lengthened but we find that 2.5 mm extension produces a suitable dent in the test panel.

    The standard does not state whether the indenter should strike the coated side or the reverse side of the test panel. Unless specified otherwise, we mount the panel so that the coated side is struck. In our experience reverse impact is a more severe test.

    After testing, the coated surface is inspected visually for cracking and loss of adhesion. A precisely defined fabric is the used to wipe the deformed area of the panel before a second visual inspection is carried out

    Sample Requirements

    Three test panels of size 100 x 50 x 1.25mm Substrate should be of burnished steel

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

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    Impact Resistance: BS 3900-E7

    Scope and Field of Application

    BS 3900-E7 is a method used to assess the resistance to the impact of a falling ball of a single coat film or multicoat systems of paint, varnish or related products.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    The only equipment required for this test is a 900 g hardened steel ball. This is dropped onto the test sample from a height of 3 metres.

    The standard does not state whether the ball should strike the coated side or the reverse side of the test panel. Unless specified otherwise, we mount the panel so that the coated side is struck. In our experience reverse impact is a more severe test.

    After testing the coating is examined for signs of cracking, flaking and detachment from the substrate.

    Sample Requirements

    At Least two test panels measuring 200 x 200 x 5mm, the substrate should be burnished steel. Unlike the other methods described, it is technically possible to carry out the test on objects other than test panels.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Impact Resistance: BS EN ISO 6272, BS 3900-E13

    Scope and Field of Application

    BS EN ISO 6272 and BS 3900-E13 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to cracking or disbondment from a substrate when it is subjected to deformation by a falling weight dropped under standard conditions.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    The equipment consists of a vertical guide tube down which falls a 1 Kg indenter fitted with 20 mm diameter hemispherical tip. The indenter can be loaded with an additional 1 Kg weight if required. A coated test panel is sandwiched between two die blocks each of which have 27 mm diameter central holes and the indentation depth of the falling weight is limited by variable stops.

    The standard states that indenter loading, drop height and indentation depth are a matters for agreement between interested parties. If no indentation depth is specified, we use 5 mm. In our experience this ensures that the resistance of the test panel to deformation is the limiting factor.

    The standard does not state whether the indenter should strike the coated side or the reverse side of the test panel. Unless specified otherwise, we mount the panel so that the coated side is struck. In our experience reverse impact is a more severe test.

    After testing the coated surface is examined using a x 10 lens and any cracking or peeling from the substrate or cracking of the substrate itself is reported.

    The equipment can be used in two modes:-

    • Pass/Fail Mode where the test is carried out using agreed values for the panel orientation, indenter loading, drop height and indentation depth.
    • Classification Mode where the test is carried out using agreed values for the panel orientation, indenter loading and indentation depth. Panels are tested using progressively increasing drop heights in order to determine the minimum drop height that gives rise to any cracking or peeling from the substrate or cracking of the substrate itself.

    Sample Requirements

    The number of panels required depends on the mode of testing selected we recommend at least 2 panels for Pass/fail mode or 5 panels for Classification mode in either case the size of the panels must be 150 x 100 x at least 0.25 mm.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

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    Impact Resistance: ASTM D 2794

    Scope and Field of Application

    ASTM D 3363 is a method of rapidly deforming by impact a coating film and its substrate and for evaluating the effect of the deformation.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    The equipment consists of a vertical guide tube down which falls a weight fitted with a handle which protrudes through a vertical slot in the tube. A graduated inch-pound scale is marked along the length of the slot. The standard specifies a number of variants of the equipment with guide tube lengths between 24 and 48 inches. The weight drops on to an indenter fitted with either a 0.5 inch or a 0.625 inch diameter hemispherical tip. The indenter tip rest against the test panel which is mounted on a die which has a 0.64 diameter central hole.

    The standard does not state whether the indenter should strike the coated side or the reverse side of the test panel. Unless specified otherwise, we mount the panel so that the coated side is struck. In our experience reverse impact is a more severe test.

    The test involves choosing the indenter size and panel orientation and then raising the weight to a height where it is expected that no failure will occur and allowing it to drop. The standard specifies three methods of examining the impacted area for cracking:-

    • visual using unspecified magnification.
    • treating with copper sulphate solution and examining for copper deposition and/or rust staining.
    • use of an electronic pin hole detector.

    The test is continued using progressively increasing drop heights in order to determine the minimum drop height that gives rise to cracking.

    Sample Requirements

    At least 5 flat coated panels measuring 150 x 100 x 0.63. The substrate should be steel.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

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    Determination of Minimum Film Forming Temperature: ASTM D 2354

    Scope and Field of Application

    Emulsion paints are formulated so that when they are applied to a substrate, the water evaporates and the resin particles that form the binder (latex) coalesce to form a continuous film. Low temperature hinders coalescence and for any latex there will be a temperature below which coalescence does not occur. This is known as the minimum film forming temperature (MFFT).

    It is generally possible to improve the coalescing properties of latices by the addition of small amounts of relatively involatile organic solvents which remain in the film long enough to soften the latex particles and aid coalescence. This approach however conflicts with environmental pressures to produce coatings which are free from volatile organic compounds (VOC's).

    It is important to emphasise that the test method described on this page only applies to latices i.e. one of the raw materials that is used to make emulsion paints. It cannot be used to determine the MFFT of emulsion paints as such. If you are interested in the film forming properties of emulsion paints, please refer to the scrub resistance tests (BS EN ISO 11998, DIN 53778: Part 2 and ASTM D 2486).

    There is no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    We carry out this determination using a Rhopoint model MFFT-90 minimum film forming temperature bar. The apparatus consists of a horizontal metal stage across which a temperature gradient can be established by means of electric heating and Peltier cooling. The temperature obtainable ranges from about -5 to 90°C.

    A film of the latex under test is cast along the stage and left to dry. A visual inspection of the dry film is then made to determine the position along the length of the film where it changes from the coalesced to the non-coalesced state. A non-coalesced film shows whitening and/or cracking. The lowest temperature at which the film is coalesced is reported as the MFFT.

    Sample Requirements

    We require no more than 100 g of sample.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

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    Determination of Water Vapour Permeability: ASTM D 1653

    Scope and Field of Application

    If a coating is applied to steel with the intention of preventing corrosion, it is advantageous for it to have minimal water vapour permeability. In contrast, an external masonry coating should be sufficiently permeable to allow water vapour to permeate through it from the interior.

    It is important to differentiate between permeability to water vapour and permeability to liquid water. Silicone masonry treatments for example are a good way of ensuring that rain water droplets run off an exterior wall rather than soak in. The treatment however does not result in the formation of a continuous coating film and consequently it has little or no effect on the permeability of the wall to water vapour.

    The test method described on this page enables the rate at which water vapour passes through films of paint, varnish, lacquer and other organic coatings to be determined.

    There is no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    The test equipment consists of a shallow metal cup (known as a Payne cup) which can be sealed using a detached film of the coating under test. In cases where it is not possible to obtain a detached film, a film can be cast on a permeable paper substrate and used as such. Detached films are preferred since although it is possible to obtain paper with very high permeability, there is always the uncertainty of the error caused by the permeability of the coating-paper interface.

    There are four ways of carrying out the test.

    • The Dry Cup Methods: The cup contains desiccant and is stored at either 50% or 90% relative humidity
    • The Wet Cup Methods: The cup contains water and is stored at either 50% or near 0% relative humidity

    We normally use the wet cup method at 23°C and 50% relative humidity. The determinations are carried out in triplicate.

    The sealed cups are weighed periodically in order to determine the amount of water vapour that has passed through the film. The weight change is plotted as a function of time until a straight line is obtained. This signifies that a steady state has been attained.

    The straight line portion of the plot is then used to determine the water vapour transmission rate in terms of grams per hour. Since the area of the circular test film can be calculated, the water vapour transmission rate of the coating can be expressed in terms of grams per square metre per 24 hours.

    If required, the permeance of the coating (in metric perms) can be calculated. The standard includes a table showing the relationship between the test temperature and the saturation vapour pressure of water. Using the appropriate value, the permeance of the coating can be expressed in terms of grams per square metre per 24 hours per millimetre of mercury.

    Sample Requirements

    We require no more than 250 g of liquid coating. Alternatively you can supply us with detached film provided it is flexible, smooth and at least 150 x 150 mm.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

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    Determination of Resistance to Liquids: BS EN ISO 2812-1

    Scope and Field of Application

    BS EN ISO 2812-1 is a method of determining the resistance of coatings to immersion in liquids other than water.

    There are no pass/fail criteria defined in the standard. These are matters of agreement between the parties concerned.

    Summary of Method

    The standard contains an annex that lists examples of liquids in which the test pieces can be immersed. These include automotive fuels and fluids as well as a selection of organic solvents, acids and bases. The tests pieces may be in the form of panels or rods. Rods are used to eliminate edge effects.

    The temperature of the liquid, the depth of immersion of the test pieces and the time of contact are all matters of agreement between the parties concerned.

    Sample Requirements

    We require three test panels each 150 x 100 mm for each coating to be tested.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

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    Determination of Resistance to Liquids: BS EN ISO 2812-3

    Scope and Field of Application

    BS EN ISO 2812-3 is a method of determining the resistance of coatings to contact with an absorbent medium impregnated with liquid.

    There are no pass/fail criteria defined in these standards. These are matters of agreement between the parties concerned.

    Summary of Method

    The standard contains an annex that lists examples of test liquids. These include the ones listed in BS EN ISO 2821-1 together with a number of viscous or paste-like materials designed to mimic those exuded by plants and animals and which can damage automotive finishes. The most notable of these is a simulated bird dropping mixture based on pancreatin.

    Panels are the only test pieces specified. The liquids are used to impregnate cotton wool or filter paper which is then held in contact with the test piece. The time of contact and the temperature are matters of agreement between the parties concerned.

    Sample Requirements

    We require three test panels each 150 x 100 mm for each coating to be tested.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Resistance to Liquids: BS EN ISO 2812-3

    Scope and Field of Application

    BS EN ISO 2812-3 is a method of determining the resistance of coatings to contact with an absorbent medium impregnated with liquid.

    There are no pass/fail criteria defined in these standards. These are matters of agreement between the parties concerned.

    Summary of Method

    The standard contains an annex that lists examples of test liquids. These include the ones listed in BS EN ISO 2821-1 together with a number of viscous or paste-like materials designed to mimic those exuded by plants and animals and which can damage automotive finishes. The most notable of these is a simulated bird dropping mixture based on pancreatin.

    Panels are the only test pieces specified. The liquids are used to impregnate cotton wool or filter paper which is then held in contact with the test piece. The time of contact and the temperature are matters of agreement between the parties concerned.

    Sample Requirements

    We require three test panels each 150 x 100 mm for each coating to be tested.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Resistance to Liquids: BS EN ISO 2812-4

    Scope and Field of Application

    BS EN ISO 2812-4 is a method of determining the resistance of coatings to contact with droplets of liquid.

    There are no pass/fail criteria defined in these standards. These are matters of agreement between the parties concerned.

    Summary of Method

    This is essentially the same method as BS EN ISO 2812-3. The same test liquids are suggested and the main difference is that they are applied to the test piece as droplets rather than impregnated absorbent material.

    Sample Requirements

    We require three test panels each 150 x 100 mm for each coating to be tested.

    If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Scrub Resistance and Cleanability: BS EN ISO 11998

    Scope and Field of Application

    BS EN ISO 11998 is a method for measuring the ability of coatings to withstand wear caused by repeated cleaning operations and to resist permanent blemishing by stains.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    BS EN ISO 11998 is the most reproducible of the three scrub test methods. The reason is that it involves measuring loss of film weight rather than the number of cycles needed to wear through the film. The reproducibility of "wear-though" methods is compromised by the difficulty in preparing films of very similar film thickness.

    The test method uses a scrub testing machine with a stroke length of 300 mm at a frequency of 37 cycles per minute. The test coating is applied to a test panel at such a thickness that the dry film can withstand 200 scrub cycles without wearing through. After drying and ageing for an agreed period, the coated panel is weighed and then subjected to 200 wet-scrub cycles. After washing and drying, it is then re-weighed in order to determine the mass loss. The mean loss in film thickness is then calculated (this requires prior determination of the non-volatile density of the coating. This is done by weighing a measured area of the dry coating. The standard defines a method for carrying out this determination).

    The mean loss in film thickness is taken as a measure of the scrub resistance of the test coating.

    The test coating is assessed for cleanability using similar test panels to those used for scrub testing. The panels are soiled (the soiling materials and the method of application is agreed between interested parties) and then subjected to the scrub test as detailed above. The panels are then assessed visually in order to determine the extent to which the soiling material has been removed

    Sample Requirements

    We require 250 ml of sample together with information regarding the film thickness at which the coating should be applied.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Scrub Resistance and Cleanability: DIN 53778: Part 2

    Scope and Field of Application

    DIN 53778: Part 2 differs experimentally from BS EN ISO 11998 but is also a method for measuring the ability of coatings to withstand wear caused by repeated cleaning operations and to resist permanent blemishing by stains

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    This test method uses a scrub testing machine with a stroke length of 430 mm at a frequency of 37 cycles per minute. While the test is designed to measure scrub resistance and cleanability at the same time it is not a very severe test and consequently can take a long time wear through the coating. The test coating is applied to a test panel so as to yield a dry film thickness of 100 microns. After ageing for 28 days, the coating is soiled using pencil, charcoal and crayon marks. This soiled sample is scrub tested and a note is made of the number of cycles needed to remove the soiling. The test is then continued until the coating is worn through (the standard includes a pictorial guide which helps to define "worn through").

    The number of cycles need to remove the soiling gives a measure of the cleanability while the number of cycles needed to wear through the coating is taken as a measure of its scrub resistance.

    Sample Requirements

    We require 250 ml of sample together with information regarding the film thickness at which the coating should be applied.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Scrub Resistance and Cleanability: ASTM D 2486

    Scope and Field of Application

    ASTM D 2486 is a method for determining the resistance of wall paints to erosion caused by scrubbing. Unlike the other two scrub tests it does not include any measurement of cleanability.

    There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

    Summary of Method

    ASTM D 2486 is a fairly severe test and consequently it does not usually take very long for the coating to wear through. This test method uses a scrub testing machine with an undefined stroke length at a frequency of 37 cycles per minute and only measures scrub resistance. The test coating is applied to a test panel using an applicator with a gap of 180 microns. After ageing for 7 days, the coated panel is scrub tested until the coating is worn through. The method also allows for the use of a reference coating which is tested at the same time. In this case the test continues until both the test and the reference coatings are worn through. In the absence of a reference paint, the number of cycles needed to wear through the coating is taken as a measure of its scrub resistance.

    If a reference coating is used, the number of cycles needed to wear through the test coating is expressed as a percentage of the number of cycles needed to wear through the reference coating.

    Sample Requirements

    We require 250 ml of sample together with information regarding the film thickness at which the coating should be applied.

    Accreditation

    PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

    Top of pagePlease contact the Testing Laboratory for further details

    Surface Energy and Contact Angle Measurements on Solids

    Scope and Field of Application

    The techniques described here are the ones that are used to measure the properties of solids (i.e. the surfaces of substrates or of dry coatings). If you are more interested in the properties of liquids, then please see "Surface Tension and Contact Angle Measurements on Liquids" on the Testing Paints Before Application page.

    The end product of any successful painting or printing process is normally a dry film of the coating on a substrate. In cases where liquid paints or inks are applied, an essential intermediate stage in the process is the formation of a satisfactory wet film of the coating. The success or otherwise of producing a satisfactory wet film depends on both the properties of the liquid coating and the properties of the substrate.

    For definitions of the relevant properties that we are able to measure please see Surface Tension, Surface Energy, Contact Angle and Adhesion.

    Dyne Pen Method

    This involves the use of a set of commercially available felt-tip pens containing a range of inks of known surface tension. One of the pens is used to apply a thin film of ink over about 7 square centimetres of the test surface. If the ink film breaks up into droplets in less than two seconds, the process is repeated using a pen filled with ink having a lower surface tension. This procedure is used to establish the lowest surface tension ink that will yield a film that remains intact for at least two seconds. The value of the surface tension of this ink is then taken as the surface energy of the test substrate.

    Sample Requirements

    This can be carried out on any surface with minimum area of 50 square centimetres

    If you wish, we can prepare the test pieces. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Contact Angle Meter Method

    In this method, a drop of a liquid of known surface tension is placed on the test surface, illuminated and then viewed through a moveable eyepiece. The eyepiece is connected to an electronic protractor which displays the viewing angle.

    The meter is constructed so that when the viewing angle equals the contact angle, the illumination viewed through the eyepiece is maximised. The contact angle and the surface tension of the liquid can then be used to calculate the surface energy of the substrate.

    This is not the most accurate method of measuring contact angles and we only recommend it in cases where you wish to determine the contact angle of a coating applied to only one side of a substrate. If your sample is coated on all sides (and does not require cutting to size) or if it is uncoated with each face having the same composition (e.g. a piece of polymer) then you should consider the tensiometer method described at "Surface Tension and Contact Angle Measurements on Liquids" on the Testing Paints Before Application page.

    Sample Requirements

    We need a panel from which we can cut a test piece 20 x 75 x less than 10 mm

    If you wish, we can prepare the test pieces. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Interfacial Tensiometer Method

    We use a Camtel CDCA-100 instrument which is a versatile computer controlled tensiometer capable of measuring surface tensions and contact angles and calculating surface energies.

    The method involves dipping the solid into and retracting it from a liquid of known surface tension. The variation of contact angle with immersion depth is measured and these values are used by the in-built software to calculate the surface energy of the solid.

    This method is restricted to solids where all exposed faces have the same composition

    Sample Requirements

    This method can only be carried on non-porous homogeneous solids. This rules out wood and also coatings applied to any substrate. It is the technique to use if you need to measure accurately (for example) the surface energy of a sample of polymer.

    We need to be able to cut a test piece 20 x 30 x not more than 5 mm.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Top of pagePlease contact the Testing Laboratory for further details

    Determination of Tensile Properties: ASTM D 2370

    Scope and Field of Application

    This method covers the determination of the elongation, tensile strength and stiffness (modulus of elasticity) of coatings when tested as free films. These values are of particular importance for coatings which are intended for application to substrates which lack dimensional stability. Examples include:-

    • masonry that is prone to cracking.
    • wood in environments where its water content can vary.
    • elastomeric polymers.
    • metallic components subject to flexure in service.

    The tensile testing methods described on this page are all carried out using detached films. If your test coatings are intended for application to metallic substrates you may wish to consider cupping or flexibility tests (BS EN ISO 1519, BS EN ISO 6860 and ASTM D 522) which can be carried out on coatings applied to substrates.

    There is no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    We carry out the determinations using an Instron Type 1026 tensile tester. This incorporates a highly sensitive electronic load weighing system with load cells employing strain gauges to detect the load applied to the specimen under test. The test specimen is clamped between two grips one of which is attached to a load cell in a moving crosshead while the other grip is fixed to the base of the tester. The crosshead is attached to two vertically mounted screws driven by a synchronous motor-gearbox assembly. The load applied to the test specimen and the distance travelled by the crosshead are both displayed on a chart recorder.

    The detached test film is condition for 24 hours under specified temperature and humidity conditions. Test specimens are cut from the film and their dimensions are recorded. A specimen is then clamped between the grips and elongated until it ruptures. The rate of elongation is between 5 and 100 percent per minute, the actual value being agreed between interested parties.

    The standard describes how the stress-strain curve is evaluated to determine elongation, tensile strength and stiffness.

    Sample Requirements

    If you are able to supply samples in the form of detached films, we require 300 x 300 mm for each coating to be tested. We can, if required, prepare detached films from liquid coatings. In this case a 250 ml sample of each coating is required together with application instructions.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Top of pagePlease contact the Testing Laboratory for further details

    Wet Adhesion: ASTM D 6900

    Scope and Field of Application

    Exposure of applied coatings to wet or humid conditions may lead to loss of adhesion to the substrates over which they have been applied. Water based coatings, especially ones that have been recently applied, may be moisture-sensitive and prone to this mode of failure. ASTM D 6900 is a method of quantifying the adhesion of emulsion paints to glossy surfaces under wet conditions.

    There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

    Summary of Method

    The method involves applying the test paint to a film of cured alkyd gloss paint on a plastic substrate. The test paint is then allowed to dry for an agreed period of time under standard temperature and humidity conditions.

    The standard defines how a lattice pattern, consisting of one set of six cuts and one set of ten cuts at right angles to each other and at set spacing, should be cut through the test paint film. This reduces the paint film within the lattice to 160 small squares of coating.

    The test piece is then immersed in water for 30 minutes, assessed for blistering and then scrub tested according to ASTM D 2486.

    The number of cycles required to produce 100% adhesion failure is recorded. If this does not occur by 500 cycles, the test is terminated and the percentage adhesion failure at 500 cycles is noted.

    Sample Requirements

    We require 1 litre of coating.

    Accreditation

    Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

    Top of pagePlease contact the Testing Laboratory for further details