ASTM D3285 Cobb Test

Testing Standard:

ASTM D3285 Test Method for Water Absorptiveness of Non-Bibulous Paper and Paperboard (Cobb Test)


ASTM D3285 is used to evaluate the materials rate of water absorption. This test method applies to most non-bibulous materials, such as paper or paperboard. Purple Diamond Testing offers ASTM D3265 Testing as part of our packaging compliance and validation services. 

The test involves placing a specimen of the paperboard into a shallow tray and adding water to the tray until the water level is above the specimen. The specimen is left in the water for a set period of time, typically 1 minute, and then removed from the tray.

The amount of water absorbed by the paperboard is then measured by weighing the specimen, subtracting the dry weight of the specimen, and reporting the result in grams per square meter (g/m2).

The Cobb test is an important measure of the paperboard’s ability to withstand exposure to water and moisture, which can affect the integrity and strength of the packaging material. It is used to ensure that paperboard meets the requirements of industry standards and regulations, as well as customer specifications for packaging performance.

According to, “1.1 This test method covers the determination of the quantity of water absorbed in a specified time by non-bibulous paper and paperboard with a minimum thickness of 0.1 mm. This test method is generally applicable to sized paper and paperboard but is not recommend as a sizing test for writing papers. The test method is based upon studies by Cobb and Loew, Cobb, and other investigators (1,2,3,4).”

The ability to resist the penetration of water in packaging is important, especially if the packaged goods are moving internationally in distribution. If this is the case, there is more time and space for the packaged product to get wet. Thus, the Cobb Test. In particular, the Cobb Test figures out the quantity of water that will be absorbed by the surface of the paper or board each time. Due to various paper and board characteristics, the test of water absorption is a function compared to the sizing and porosity of the paper and board being evaluated. This test is often involved in obtaining certain certifications such as those that involve hazardous materials packaging. The standard method is useful when evaluating a different variety of hygroscopic surfaces that are originally designed to resist water absorption.

Manufacturers, suppliers, and consumers of paper and paperboard products benefit from this test as it provides valuable information about the quality, consistency, and suitability of these products for various applications. The test helps ensure that the paper and paperboard products meet the required standards for their intended use, such as printing, packaging, and labeling. Additionally, the ASTM D3285 Cobb test can be used by researchers and academics to further their understanding of paper and paperboard product development and manufacturing processes.

Rationale for ASTM D3285:

Test Method for Water Absorbency of Non-Bibulous Paper and Paperboard (Cobb Test). The amount of moisture in paper materials affects the overall physical strength, porosity, and end useability. This test method can be ideal when comparing varied materials or verifying a material is within a specified range of acceptance. A predetermined volume of water is applied to the material and the time it takes to be absorbed is recorded. 

According to, “The Water Absorption Apparatus, to permit one side of the specimen to be wetted uniformly at the moment the soaking period begins, and to allow controlled rapid removal of the water from the specimen at the end of the test period. The cross bar has a hole at one end and a slot at the other to ease assembly and use. On the base plate is a rubber mat, larger than the outside dimensions of the ring, on which the specimen is clamped.”

The metal parts should preferably be of brass or other corrosion-resistant material. Several versions of the water absorption apparatus are now available. Although the basic procedure for performing the test is not changed, the clamping mechanism is. This may affect the time required to remove the specimen from the apparatus.” Other materials for this testing method may include a metal roller, a timer, a graduated cylinder, and a balance. The balance will have an accuracy of 0.01 g or better.

Key Points for ASTM D3285:

Related Standards:

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