Assessment of Chalking

BS 3900-H6 : ISO 4628/6

 Chalking Test

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 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.

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

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 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.

 

Please contact Peter Collins for further details.

 

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