Cobb Testing Paper & Packaging Material- Significance & Procedure

Cobb testing refers to the process of determining the water quantity that can be absorbed by a paper, corrugated paperboard, etc., in a given time and under standard conditions. It is performed through a cobb sizing tester, which also gives a lot of information about the characteristics of paper, including porosity, sizing, etc.

Before sending the paper for its end use, every paper goes through this test. Why? Let us understand in the following section.

Why Cobb Test Is Performed?

Cobb Testing is done to check the water resistance capacity of the paper or paperboard. Since paper is a hygroscopic material, it can attract and hold water present in the surroundings. Hence, knowing its ability to resist water is important. This test also measures the quantity of water that the paperboard can absorb in a given time. If the paper/board absorbs too much water, the box will not be able to maintain strength and integrity, resulting in breakage. Hence, this deteriorated packaging will be a problem if the product is heavy or contains harmful goods.

When the test is performed, a Cobb value comes in the result. A high cobb value indicates that the paperboard has the ability to absorb and retain moisture. Whereas a low value means that it is resistant to water absorption and retention. The cobb value has to be maintained as per the paper or board requirements. This value guides manufacturers to use the right materials for packaging.  

How Cobb Testing Is Performed?

Cobb Testing is done using the cobb sizing tester. This instrument checks the water absorption quality of the paper or packaging material, so as to prevent any damage caused to the products later on. The following steps are performed in the process:

1. Place a sample with blotting or bibulous papers between the sliding pad and pivotal cylinder.
2. Tighten the sample with the screw and then turn down the cylinder to its position. 
3. Add 100 ml of water into the cylinder. A self-starting digital timer is attached to the instrument to record the absorption time. This starts automatically as soon as the cylinder is turned down to perform the test. The time can range from 1 to 10 minutes for single to multilayered boards. 
4. Once the test completes, remove the water from the cylinder and also take out the sample.
5. Use the built-in couch roller to remove any excess water. Move the roller forward and backward once to do that. 
6. Now weigh the sample on a digital weighing machine. 
7. Calculate the cobb value now by subtracting the weight of the sample before the test from the after-test weight. 

As mentioned in the previous section, this value will determine the water absorption and resistance ability of the sample. The cobb test is a speedy process that gives accurate results. It is performed to test the water absorbency of paper, paperboard, and similar materials.

Conclusion

Cobb tester is a highly effective paper testing machine by UEC. We are manufacturers, suppliers, and exporters of paper, pulp, and packaging testing machines. Visit the website to explore more about these instruments and get in touch for inquiries.