The opacity of paper refers to the degree to which paper blocks light under certain lighting conditions, and generally refers to the ability of paper to block light. There are two main methods of measuring paper opacity:
Comparison Method: This is a method of directly comparing the light transmittance between two samples, usually using a Colorimeter to measure the difference in light transmittance between the two samples to calculate the opacity. This method needs to use a set of standard reference samples, and determine the opacity value of the sample to be tested by comparing with the standard reference samples.
Diffuse reflection method: Diffuse reflection method is one of the commonly used methods to measure the opacity of materials. Its basic principle is that when light shines on the surface of a material, it will be scattered into various directions, which is called diffuse reflection. By measuring the intensity of the diffuse light and the intensity of the incident light, the opacity of the material can be calculated. Usually measured with an optical measuring instrument such as a diffuse reflectance photometer.
The measurement results of opacity are affected by many factors, including paper quality, lighting conditions, measurement methods and instruments, etc. Therefore, care should be taken to control these factors during measurement to ensure the accuracy of measurement results.
