Determination of Surface Drying Time

BS 3900-C2 : ISO 1517

 Surface Dry Test

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.

The actual standard is a copyright-protected document and we are not able to provide you with copies. If required however, you can easily obtain copies from the British Standards Institution.

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.

 

Please contact Peter Collins for further details.

 

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