The ability of a hygroscopic material to resist the penetration of water is referred to as a Cobb test. Specifically, this test permits the determination of the quantity of water that can be absorbed by the surface of paper or board in a given time. Water absorption is a function of various paper and board characteristics such as sizing, porosity, etc.
This test is required for certain certifications such as those involving hazardous material packaging. Is a useful procedure for a variety of different hygroscopic surfaces that are designed to resist water absorption.
This test is not intended to be used for precise evaluation of the writing properties of paper although it does give a general indication of suitability for use with aqueous inks.
(3) Cobb test fixtures and facilities