The whiteness and yellowing value of pulp is an important index to measure the color of paper, and its determination method is as follows:
Pulp whiteness measurement: Usually, the CIE Lab color space measurement method under the standard light source D65 lighting condition is used to measure the L value of the pulp sample, and then the whiteness value of the pulp is calculated according to the standard color plate comparison. Commonly used instruments are Colorimeters, photometers, etc.
Determination of pulp yellowing value: Put the sample to be tested and the standard whiteboard under the long-wave ultraviolet lamp for a certain period of time, and then measure the b* value of the sample with a color difference meter or photometer, and then calculate the yellowing value. The standard light box or standard light source comparison method can also be used to compare the sample to be tested with the standard white board, and calculate the yellow return value according to the color difference.
Beichao reminds you: During the measurement process, you should pay attention to standard operations, maintain the consistency of measurement conditions, and avoid measurement errors. At the same time, attention should be paid to the preparation and storage of samples to avoid the influence of external factors on the color of samples.
