SAMPLING
In the first place you should carefully sample your glue with a view to testing.
Take several samples from various parts of the barrel. Flake glue is often made up of different varieties, and a single sample may not be at all representative. Ground glue, from its very nature, is easily adulterated. It should be examined in a good light, for evidence of foreign substances. Examine flake glue carefully also for uniformity of odor and general appearance. If glue has been adulterated while in original form it is practically impossible to determine the adulteration by external appearance. Subsequent adulteration may be detected.