Sized Paper or Non-bibulous paper are those which are not designed to deliver high rate of water absorption quality but must deliver a particular amount resistance towards water. Paper such as tissue papers, or blotting are bibulous in nature which means they have high water absorptions strength. However, non-bibulous paper are not manufactured that way but still it must ensure that it has a specified amount of water absorption quality. Equipment like Cobb tester are used to evaluate the Cobb value of such specimen by using TAPPI based test method.
The apparatus used as per TAPPI Standard must include a device which allow one side of the paper to be drenched in water uniformly when the soaking process is initiated. Also allow to remove the water rapidly at the end of the test. Cobb Tester is a corrosion resistant body with faster locking mechanism. Along with TAPPI it also complies with IS 1060.