This test method provides a simple quantitative measure of water absorption by coated composite wood products. Although primarily used to evaluate factory-primed composite wood products, this test method may be of service for other wood substrates and coating systems.

This test method has demonstrated utility for composite wood siding products ranging in thickness from approximately 6.35 to 25.4 mm (¼ to 1 in.). Extension of this test method to wood substrates of other types and thickness may be useful.

Conditioning of substrate, coated sample preparation, application method, dry film thickness, cure conditions, and number of replicate specimens should be agreed upon between the purchaser and the supplier of the coating material.

Such measurements are used as indicators or predictors of the anticipated performance of coated composite wood products during exterior exposure. They may be used for developmental evaluation of coatings, substrates, or both. They may also be useful for quality control or monitoring of the production of coated composite wood products.

1.1 This test method is intended to serve as a means for measurement of liquid water that passes through a wetted paint film, and which is subsequently absorbed and retained by the underlying wood substrate. Alternative techniques for the use of the “Cobb Ring” apparatus are described.

1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.