5.1 This test method is intended to differentiate between the exterior durability of two or more adhesives. At present, this is done by comparing the adhesives as described in 4.5 and 4.6 rather than by assigning absolute numerical values for durability performance.

5.2 The test method as described is for comparing potential long-term durability rather than for use as a quality control procedure. This makes it suitable for research, adhesive evaluation, process evaluation, and product design. A modification could be made, that is, shorten the number of cycles used so the test method would be suitable for quality control in production mills. The results obtained for a particular adhesive can be used to show how many cycles are required for a mill quality control test of that adhesive.

5.3 The test method assumes that boil/dry cycling is an adequate and useful accelerated aging technique. Evaluation of long-term durability of adhesives in wood joints under severe service conditions, including extended exterior exposure, is a complex field, and no entirely reliable short-term test is known to ensure that a new type of adhesive system will satisfactorily resist all of the chemical, moisture, microorganism, and solvent effects that such severe service may involve. Except for effects of microorganisms and other similar biological influences, this test method has proven very useful for comparison purposes to distinguish between adhesive systems of different degree of durability to the usual temperature, moisture, and cyclic moisture conditions. It has proven very useful to distinguish between bondlines, made with adhesives of proven chemical and biological durability, that were properly used in production to resist the mechanical and moisture effects that such joints must withstand in severe service over extended periods of exposure. It does not, in itself, assure that new types of adhesives will always withstand actual exterior or other severe service.