ISO 535 Paper and Cardboard - Determination of Water Absorbency - Standard Test for the Cobb Method

ISO 535 specifies a method for determining the water absorbency of sized paper and board, including corrugated board, under standard conditions. It may not be suitable for paper weighing less than 50 g/m2 or embossed paper.

Not suitable for porous papers such as newsprint or unsized papers such as blotter paper or other papers with relatively high water absorbency for which ISO 8787 is more suitable. Although this method gives a general indication of suitability for use with aqueous inks, it is not intended to be used for conclusive evaluation of the writing properties of paper.

Any apparatus can be used that allows:

• Immediate and uniform contact of water with the part of the test piece under test;
• Controlled rapid removal of unabsorbed water from the test piece at the end of the contact period;
• Quick removal of the test piece without the risk of contact with water outside the test area.

In its simplest form, the apparatus consists of a rigid base with a flat, planar surface and a rigid metal cylinder with an internal diameter of 112,8 mm ± 0,2 and clamping tightly to the base plate. The edge of the cylinder in contact with the test piece must be flat and properly machined to a thickness that will prevent the cylinder from entering the test piece. The height of the cylinder does not matter, provided it contains a water depth of 10 mm.

If testing is done to evaluate the lot, the sample will be selected in accordance with ISO 186. If testing is performed on another sample type, ensure that the samples drawn are representative of the sample drawn.

EUROLAB assists manufacturers with ISO 535 test compliance. Our test experts, with their professional working mission and principles, provide you, our manufacturers and suppliers, the best service and controlled testing process in our laboratories. Thanks to these services, businesses receive more effective, high-performance and quality testing services and provide safe, fast and uninterrupted service to their customers.