ISO 535 pdf download Paper and board — Determination of water absorptiveness — Cobb method
This International Standard specifies a method of determining the water absorptiveness of sized papeland board, including corrugated fibreboard, under standard conditions.lt may not be suitable for paperofgrammage less than 50 g/m2 or embossed paper. It is not suitable for porous papers such as newsprintor unsized papers such as blotting paper or other papers having a relatively high water absorptivenessfor which ISO 8787 is more suitable.
This method is not intended to be used for precise evaluation of the writing properties of paper althoug!
it does give a general indication of suitability for use with aqueous inks.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and areindispensable for its application, For dated references, only the edition cited applies. For undatedreferences, the latest edition ofthe referenced document (including any amendments) applies.
ISO 186, Paper and board – Sampling to determine average quality
ISO 187, Paper, board and pulps — Standard atmosphere for conditioning and testing and procedure formonitoring the atmosphere and conditioning of samples
ISO 5269-1, Pulps — Preparation of laboratory sheets for physical testing – Part 1: Conventional sheetformer method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply
water absorptiveness (Cobb value)calculated mass of water absorbed in a specified time by 1 m2 of paper or board under specifiedconditions
Note 1 to entry: The test area is normally 100 cm2
A test piece is weighed immediately before and immediately after exposure for a specified time of onesurface to water, followed by blotting. The result of the increase in mass is expressed in grams persquare metre(g/m2).
5 Reagents and materials
5.1 Water, distilled or deionized.The temperature ofthe water is important and should be maintainedduring the test at the temperature used for conditioning and testing.
5.2Blotting paper, having a grammage of 250 g/m2 + 25 g/m2. Pulp evaluation blotters are acceptablefor the purposes ofthis International Standard (see ISO 5269-1).
6.1 Absorptiveness tester for the determination of water absorptiveness.
Any type of apparatus may be used which permits
— an immediate and uniform contact of the water with the part of the test piece submitted to the test;— controlled rapid removal of the unabsorbed water from the test piece at the end of the contact
— the rapid 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 smooth, planar surface, and a rigid metal cylinder of 112,8 mm ± 0,2 mm internal diameter (corresponding to a test area approximately 100 cm 2 ) and with a means of clamping it firmly to the base plate. The edge of the cylinder in contact with the test piece shall be flat and machined smooth with a thickness sufficient to prevent the cylinder cutting into the test piece. The height of the cylinder is not important provided it is sufficient to contain a water depth of 10 mm.