Durability

These tests are designed to measure the effect of sunlight, moisture and temperature on surface coatings applied to a variety of substrates. If you are more concerned with the way that surface coatings protect substrates from corrosion, please refer to our Corrosion Resistance tests.

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.

Artificial Weathering using a Fluorescent Lamp Source: ASTM G154

Scope and Field of Application

This is a method for determining the resistance of materials to artificial weathering and deals with the testing of non-metallic materials. This means the standard can be used both for paints and other organic materials such as polymers.

Like all laboratory tests, there are advantages and limitations to weathering under artificial conditions. The test method is relatively cheap and simple to carry out however, the fluorescent lamps defined by the standards are not a good approximations to natural sunlight. The difference is greatest at wavelengths above 350 nm.

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 can be carried out using two different types of instrument which allow for different types of exposure cycle. The basic instrument allows for periods of either lamp illumination or water condensation on the test panels. The more advanced instrument can also provide a water spray.

The standard defines eight different exposure cycles in terms of lamp type, irradiance, black panel temperature and the periods of illumination and wetness. The standard also states which cycles have been used for testing surface coatings and plastics in general, automotive paints, roofing materials and wood finishes. In fact any exposure conditions can be used provided they are detailed in the test report. We will be pleased to advise on the most appropriate conditions for testing your materials.

In our experience when exterior alkyd gloss paints are exposed in the test cabinet for 1,000 hours they undergo a loss of gloss equivalent to 1 year of natural exposure in Southern England when a cycle of 4 hours illumination at 60°C followed by 4 hours condensation at 50°C was used.

Our instruments are manufactured by Q-Panel Lab Products and their website includes full details of all their products

Sample Requirements

Ideally we require 150 x 75 mm panels not more that 5 mm thick, although we can accommodate a limited number of 150 x 100 mm panels provided they are less than 5 mm thick. If you have smaller samples you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

We recommend running samples in triplicate.

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.

Artificial Weathering using a Fluorescent Lamp Source: ASTM D 4587

Scope and Field of Application

This is a method for determining the resistance of materials to artificial weathering and deals with the testing of paint and related coatings

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 deals with the selection of test conditions, the preparation of test specimens and the evaluation of results. It is intended to be used in conjunction with ASTM G 154 or BS EN ISO 11507:BS 3900-F16.

Sample Requirements

Ideally we require 150 x 75 mm panels not more that 5 mm thick, although we can accommodate a limited number of 150 x 100 mm panels provided they are less than 5 mm thick. If you have smaller samples you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

We recommend running samples in triplicate.

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.

Artificial Weathering using a Fluorescent Lamp Source: BS EN ISO 11507, BS 3900-F16

Scope and Field of Application

BS EN ISO 11507 and BS 3900-F16 are alternative names for the same method which deals with determining the resistance of paint and related coatings to artificial weathering.

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 is identical to that specified for ASTM G154. The only significant difference is that BS EN ISO 11507 / BS 3900-F16 only defines one set of exposure conditions for use in the condensation mode. The conditions are a cycle of four hours at 60° C (dry) followed by four hours at 50° C (wet). The BS standard does not define any cycles for the spray mode. These are a matter for agreement between interested parties.

Sample Requirements

Ideally we require 150 x 75 mm panels not more that 5 mm thick, although we can accommodate a limited number of 150 x 100 mm panels provided they are less than 5 mm thick. If you have smaller samples you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

We recommend running samples in triplicate.

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.

Artificial Weathering using Oxygen Plasma Erosion

Scope and Field of Application

Work carried out by PRA has shown that when paint films are exposed to a low temperature oxygen plasma they degrade in a manner similar to that observed during natural exposure.

The oxygen plasma erosion method provides very fast results and is relatively cheap when compared to other weatherometer tests. Weathering equivalent to years of natural exposure can be carried out in hours rather than weeks or months. It should be emphasised however that this method is still in the development stage and is not supported by any national standard. The operating conditions of the plasma chamber need to be established for each type of paint tested and only a few small samples can be tested simultaneously.

Summary of Method

The test is carried out using a Polaron Model PT 7300 Plasma Barrel Etcher that is designed for the oxygen plasma erosion of samples prior to examination using scanning electron microscopy. Polaron is now owned and managed by Quorum Technologies and they can supply equipment of this type.

The test sample is placed in the chamber which is then evacuated and refilled with oxygen at low pressure (approximately 0.2 mbar). Radiofrequency power (50 to 150 watts at 13.56 Mhz) is then fed into the chamber via capacitor plates in order to generate an oxygen plasma.

Once the experimental variables of radiofrequency power, gas composition and pressure have been decided a number of coated panels are produced for each system under test and these are exposed sequentially for increasing periods of time ranging from 5 to 90 minutes. The degree of degradation of the coatings is then measured either by gloss or degree of chalking. A plot of gloss or chalking versus time is then produced. Comparison of these plots enables the relative rates of degradation of the test systems to be compared.

All our experience to date has shown that it is not possible to create one set of conditions that is applicable to all classes of coatings. What we have been able to do is adjust the conditions so that we can replicate the degradation that occurs when the same class of coatings are exposed at the same location.

We have shown, for example, that this method is better than Q-UV weathering at predicting the exterior durability of polyester powder coatings. The oxygen plasma method produced in 90 minutes a degree of degradation equivalent to about 1 year in Scandinavia. This compared with the 2000 hours needed for the Q-UV method.

Sample Requirements

The technique involves exposing the samples to an oxygen plasma at low atmospheric pressure. Consequently it is best to avoid samples that have significant amounts of residual volatiles or entrapped air. We can test samples on wood provided they can be supplied as coated strips no more than 3 mm thick. Samples on paper are no problem but metal panels tend to heat up 80°C in the chamber. We have found glass microscope slides (76 x 51 mm) to be the ideal substrate. Samples should not be smaller than this. The maximum size is 150 x 100 mm x 10 mm. We require 12 panels for each sample to be tested.

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.

Artificial Weathering using a Xenon Arc Source: BS EN ISO 11341

Scope and Field of Application

BS EN ISO 11341 is a method of determining either the lightfastness of paint films and allied materials or their resistance to artificial weathering. It aims to replicate the degradation caused by sunlight (either direct or through window glass) and rainfall.

The xenon arc source, when used in conjunction with appropriate filters, is generally regarded as giving the closest approximation to natural sunlight that can be obtained in the laboratory. The equipment also allows for a greater degree of control of temperature, humidity and radiation dose than is possible with other forms of accelerated weathering. This is one of the most expensive weathering tests and is limited to test samples that are flat.

An alternative and less expensive method of measuring lightfastness involves the use of a fluorescent lamp weatherometer. Please refer to lightfastness test method for details.

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

Summary of Method

The equipment consists of a chamber in which test samples are mounted on a circular carousel which rotates around a xenon arc lamp. A number spray nozzles are positioned in the chamber so that, if required, they can wet the test surfaces of the panels. The parameters that can be controlled and monitored include black panel temperature, humidity, irradiance, light-dark periods and wet-dry periods.

The standard defines four different operating conditions, two for lightfastness testing and two for resistance to artificial weathering. The lightfastness testing is carried out dry using optical radiation filters equivalent to terrestrial solar radiation through 3 mm thick window glass. Artificial weathering testing is carried out using wet / dry cycles and optical radiation filters which transmit a spectral range close to that of terrestrial solar radiation.

Sample Requirements

We require 150 x 75 mm samples not more that 5 mm thick. If you have smaller samples, you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

We recommend that samples are run in triplicate.

Artificial Weathering using a Xenon Arc Source: ISO 12040

Scope and Field of Application

ISO 12040 is a method similar to BS EN ISO 11341 but is used for determining the lightfastness of printed material, printing inks and substrates (paper, board, metal and plastic) used in printing processes

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

Summary of Method

The standard defines one set of operating conditions which are used to measure the lightfastness of printed material, printing inks and substrates. A pane of plate glass is placed between the light source and the test piece. The thickness and composition of the pane is such that it absorbs all wavelengths below 310 nanometres and has at least 90% transmission between 380 and 700 nanometres. The intention is to simulate the effect of sunlight through window glass.

The sample is exposed until it has undergone a distinct colour change. Blue Wool Scale standards are exposed at the same time. At the end of the exposure period the Blue Wool Scale standards are examined in order to determine which one has faded to the same extent as the sample. The Blue Wool scale is made up of eight standard ranging in lightfastness from Number 1 (very poor) to Number 8 (outstanding).

Sample Requirements

We require 150 x 75 mm samples not more that 5 mm thick. If you have smaller samples, you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

We recommend that samples are run in triplicate.

Assessment of Lightfastness

Scope and Field of Application

Lightfastness is a term used to describe the resistance of a material to colour change when exposed to sunlight or to artificial light sources. When paints are exposed outdoors they generally become less glossy and more prone to cracking and flaking; they may also show colour changes or fading. Paints exposed indoors to sunlight that has passed through window glass generally degrade less rapidly the reasons being that they are not exposed to rainfall nor to the ultraviolet region of the solar spectrum ( glass does not transmit very much UV radiation).

In addition to paints, we can test other coloured items including printed material, textiles and plastics and these can be exposed directly to the light source or tested behind glass.

Summary of Method

We offer an in-house method based on the Q-UV fluorescent lamp weatherometer. In our experience, when this equipment is fitted with Q-UVA lamps, it takes between 400 and 500 hours to producing fading equivalent to 6 months natural exposure behind window glass in the UK.

We use the Blue Wool Scale method to quantify the radiation dose and as a general guide, a sample of Blue Wool Number 7 fades to Grey Scale 4 after one year of natural exposure behind window glass in the UK.

This method is only suitable for quantifying internal exposure. If you require lightfastness tests to be carried out on samples intended for exposure outdoors, please consider the advantages and limitations of our fluorescent lamp and xenon arc methods for artificial weathering.

In addition to our in-house method, we offer a British Standard method based using xenon arc equipment.

Sample Requirements

Ideally 150 x 75 mm panels not more that 5 mm thick, although we can accommodate a limited number of 150 x 100 mm panels provided they are less than 5 mm thick. If you have smaller samples you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

We recommend that samples are run in triplicate.

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.

Controlled Temperature and Humidity Exposure

Scope and Field of Application

This method can be used to give an indication of how well a painted surface will resist a wide range of temperature/humidity conditions. If you are particularly interested in resistance to exposure to warm humid conditions, please refer to the Resistance to Humidity tests on the Corrosion Resistance page. Coatings intended to resist prolonged contact with water can be tested using our Resistance to Liquids tests described at Mechanical Properties.

Summary of Method

Samples are exposed in a Fisons Climatic Cabinet which is essentially a chamber mounted above an air treatment assembly containing a heating element, a chilled water operated heat exchanger, water atomisers and an air recirculating system. The chamber is equipped with temperature and humidity sensors together with an electronic control and recording system.

We can use this equipment to test the resistance of coatings to temperatures in the range from -5 to +50 °C and humidity. In practice, not all possible combinations of temperature, relative humidity can be attained we will be pleased to advise you as to the range of relative humidity obtainable within a chosen temperature range. The cabinet can be maintained at one set of conditions or it can be cycled, for example, between hot/humid ( 40°C and 95%+ RH ) and cold/dry ( 20°C and 70% RH ).

One consequence of the versatility of the equipment is that there are numerous standard methods of operation. We can select from BS, ISO, DIN and ASTM methods for the testing of paints, varnishes, plastics, rubbers, bituminous materials and printed items and we will be pleased to advise on the most appropriate conditions for testing your materials.

Sample Requirements

The chamber dimensions are 80 x 80 x 86 cm and we can accommodate any number of samples that will fit within this chamber provided that their total weight does not exceed 20 Kg.

We recommend that samples are run in triplicate.

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.

Natural Weathering BS EN ISO 2810

Scope and Field of Application

Natural weathering of paints and similar materials involves exposing test panels outdoors at appropriate locations. These locations can be chosen on the basis of climate ( eg tropical, temperate, desert ) or on the basis of atmospheric pollution ( eg rural, industrial, marine).

Natural weathering has the single important advantage that, for a given location, it provides the most reliable data on how a coating will perform in service. However If the coatings under test are highly durable, it can take years to obtain sufficient degradation to enable them to be differentiated and as no two years are the same consequently you can never reproduce the results you obtain.

BS EN ISO 2810 is essentially a guidance note for the conduct of natural weathering tests. There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

Summary of Method

We follow the general principles of BS EN ISO 2810 and we can expose test panels at rural, urban, industrial and marine sites. We can, if required, monitor the relevant exposure conditions at regular intervals.

We recommend that the panels are assessed every six months. Normally we would rate the coatings for blistering, chalking, cracking, flaking, microbial growth and (if on steel) for rusting. There are however a number of additional mechanical and/or optical tests that would normally be carried out. Please bear in mind that for most of these additional tests, the panels have to be returned to our laboratory. Some of these laboratory tests are destructive so it is necessary to have sufficient panels on exposure to allow for this.

Sample Requirements

BS EN ISO 2810 requires that each test panel shall have an area of at least 300 square cm and that no side should be less than 10 cm in length. We normally use 10 x 30 or 15 x 20 cm panels (4 x 12 or 6 x 8 inch). We recommend that panels should be exposed in triplicate together with extra panels, if required, to allow for any destructive testing.

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.

Resistance to Temperature Change: ASTM D1211

Scope and Field of Application

ASTM D1211 is a method of determining the resistance to cracking of clear nitrocellulose lacquer films applied to wood or plywood substrates and subjected to sudden changes from high to low temperature. We can test to this standard or we can use it as a basis for tests involving different coatings and substrates.

If you are concerned with the resistance of liquid coatings to changes in temperature then please refer to the Freeze-Thaw test described at Testing Paints Before Application.

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

Summary of Method

Coated test panels are placed in an oven at about 50° C for 1 hour and then transferred to a refrigerator and stored for 1 hour at about minus 20° C. The panels are then left at room temperature for 15 minutes before being assessed for cracking. The whole process is then repeated for an agreed number of cycles or until a defined density and size of cracks is observed.

Sample Requirements

The panels defined in the standard are 300 x 150 x 8 mm cut from plywood. We can test panels of this size (or smaller) cut from any substrate. At least 3 panels are required for each 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.

Back to

Independent Testing

Laboratory Services

Register your current R&D interests and expertise to potentially benefit from participation in new grant funding proposals for collaborative research projects.