The resistance to water penetration is determined by the quantity of water absorbed by a paper or a board when one of its faces is placed in contact with this liquid, under the conditions.
Cobb Tester consists of a brass (or gun metal) cylinder of known inside diameter and length. It has a metallic plate, which is used for clamping the one side of the cylinder with the help of bracket and bolts. The metallic plate, which is used for clamping purpose, is paste a rubber sheet for the perfect clamping. The whole assembly of the cylinder and clamping arrangement is pivoted so that easy and fast pour off the water takes place. A brass roller of specified size and shape is also provided with the instrument. The equipment is designed to give a long and trouble free life; the components are bright polished and bright chrome platted.