Cobb Tester

COBB TESTER – WATER ABSORPTION TESTER

The cobb tester is a simple instrument which measures the water absorptiveness of paper, cardboard and corrugated fibreboard under standard conditions. The cobb sizing test is used worldwide to test absorption or resistance to absorption of water, oil and other liquids.

The Cobb test determines the amount of water absorbed into the surface by a sized (non-bibulous) paper, paperboard, and corrugated fibreboard paper or paperboard sample in a set period of time. Water absorbency is quoted in g/m2.
The water absorbency of a material can have strong influence on printability and the setting rate of water based adhesives.
The Cobb value provides information about the water absorption capacity of cartonboard samples. The Cobb test determines the amount of water that is taken up by a defined area of cartonboard through one-sided contact with water, within a certain amount of time. Depending on the material, contact times of 60, 180 and 1800 seconds are common. To achieve certain Cobb values the cartonboard needs to be sized. Additives, so-called sizing agents, are added or applied either by mass sizing or surface sizing, which cause a partial hydrophobising.

Why Cobb Testing? 
Cobb tests are performed, because paper and fiberboard tend to attract and hold water molecules from the surrounding environment. The Cobb test is essential as it tests the ability of the paper to resist the penetration of water and quantity of water absorbed by the surface of fiberboard.

What is Cobb value?
The Cobb value provides information about the water absorption capacity of cartonboard samples. The Cobb test determines the amount of water that is taken up by a defined area of cartonboard through one-sided contact with water, within a certain amount of time.

How do you find the Cobb value of a paper?

Weigh the sample & Now subtract the dry weight from the wet weight, the value you have is the Cobb value of Kraft paper. This the amount of water the sample absorbed in a defined time period.