Cobb Value

General information 

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.

Additional details – practical relevance

For packaging that is exposed to high moisture levels, it makes sense to use board grades with a low Cobb value (sized grades). The lower the Cobb value (low water absorption), the more stable the package remains even at high humidity.