Paint Color Difference Measurement and Evaluation
After using the formulated paint to paint the wall, color difference often occur. There are two main methods for measuring and evaluating color difference: visual method and color difference meter. Many people still use the traditional color difference evaluation method-the visual method. In order to standardize the evaluation standard of paint color difference, we usually use professional color measuring instrument-color difference meter.
I. Causes of paint color difference
The substrate is not flat and the wall absorbs the paint unevenly.
The paint is over-diluted. Each time the paint is mixed, the ratio of paint to water is different, resulting in a different paint consistency.
The construction is unprofessional. The quality of the tools used during the painting process is poor, resulting in uneven paint during painting.
The same paint may have color difference due to different batches and different processing plants.
II. Paint color difference measurement and evaluation
1. Visual method: Simply put, it is to directly observe the color with the human eye to see if there is any color difference and compare it with the CIE (International Commission on Illumination) standard chromaticity diagram. The basis of visual evaluation is standard light source. Standard light sources include: D65 light source, incandescent lamp, cool white fluorescent lamp. The light source has a great influence on the visual results and the color difference of objects under different light sources will be different. In addition to the standard light source, many factors such as the observer's viewing direction and the distance between samples will also affect the visual results. This evaluation method is very subjective. The accuracy of the measurement results is low and the measurement efficiency is also low.
2. Color difference meter: The colorimeter is a professional color measuring instrument and different colorimeters use different principles. 45° ring illumination principle or the integrating sphere principle. Measure the tristimulus value xyz of the sample through integration and then calculate the chromaticity coordinates and other parameters of the sample. The detector is usually covered with a filter to correct the relative spectral sensitivity of the detector to the spectral tristimulus value recommended by CIE. When such three light detectors are used to receive light stimulation, the tristimulus values x(λ), y(λ), z(λ) of the sample can be measured with one integration. The filter must meet Luther's condition to accurately match the light detector.
Compared with the visual method, the measurement result of the colorimeter is more objective and accurate. In addition, some advanced portable color meters on the market can also be connected to the mobile App via Bluetooth. The measured color can be saved in the mobile App, so that it can be directly compared with the sample color next time.