The Cobb Absorbency Tester is a laboratory instrument based on the Cobb test method for evaluating the surface water absorption properties of paper and cardboard. This article details the working principle, technical characteristics, test process and wide application of the instrument in the paper products industry.The water absorption of paper and cardboard is an important indicator that affects their performance and use, especially in the fields of packaging, printing and writing. By measuring its water absorption, it is possible to understand the degree of sizing and the quality of the surface treatment of the paper. The erection Tester is widely used because of its high test accuracy and easy operation.
How it works
Based on the Cobb test method, the absorbency Tester evaluates the surface water absorption performance of the sample by contacting it with a certain volume of water for a specific time to determine the amount of water it absorbs. The core principles are as follows:
The specimen is in contact with a specific area of water to simulate the water absorption process in the actual use environment.
At the end of the test, the mass change of the sample after water absorption is quickly weighed, and the water absorption value (unit: g/m²) is calculated.
Through the analysis of the average value and standard deviation of multiple groups of samples, the uniformity and stability of the paper surface can be effectively evaluated.
Technical features:
Metal cylinder design – 100 ± 0.2 cm² inner cross-section to ensure a consistent test area.
Smooth rollers – width 200 ± 0.5 mm, mass 10 ± 0.5 kg ensure uniform moisture removal.
High-precision accessories – including balances with a sensitivity of 0.001 g, stopwatches with a reading accuracy of 1 second, and other auxiliary tools.
Absorbent paper requirements – Stable water absorption, 200–250 g/m² quantitative, can be used multiple times.
Test process
Specimen preparation
Paper or cardboard is cut into round specimens with a diameter of 125 mm, ensuring that each specimen has an area of 100 cm².
Water contact time selection
According to the test requirements, select the appropriate water absorption time (e.g. 30 seconds, 60 seconds, etc.).
Weighing & Calculating
Record the quality of the specimen before and after water absorption.
Use the formula C=(G2-G1)×100 to calculate the erection value.
Data Logging
The average and standard deviation of the test results are calculated to generate a final report.
Fields of application
packaging industry
The water absorption of corrugated cardboard and packaging paper directly affects its moisture resistance and load-bearing capacity.
Printing industry
By testing the water absorption of the paper surface, the sizing process can be optimized and the ink adhesion performance can be improved.
Paper R&D and quality control
As a routine test method, it can be used for the development of new types of paper and for quality control in the production process.
Precautions
Not suitable for extremely absorbent or uneven sizing (e.g. newsprint, blotting paper).The test process should avoid operator errors and ensure accurate control of the contact time between the specimen and the water.After the test, the instrument needs to be cleaned in time to keep the equipment dry and prolong the service life.
As a professional equipment for evaluating the water absorption performance of paper and cardboard surfaces, the erection Tester has played an important role in production and experiments. Through accurate test data, enterprises can better control product quality and improve market competitiveness.
