color
Color is people's visual perception of objects. The so-called vision is the reflection caused in the brain after the light of different wavelengths stimulates people's eyes. The color of the coating film is the color that is reflected or transmitted from the surface of the coating film and enters the eyes after absorption, reflection, refraction and other effects when light hits the coating film. The factors that determine the color of the coating film are the light source, the nature of the coating film itself and human vision. There are visual and instrumental methods for measuring the color of paint films. This article describes the methods and steps for visually measuring the color of paint films.
Scope and description
This method is applicable to the visual colorimetric comparison of paint and product coating color. The test principle is to compare the color difference between the sample template and the standard template or standard Color Chart by visual inspection under certain light source conditions.
Instruments and Materials
Visual color comparison box: as shown in the figure below
test methods
(1) Observation under natural sunlight Under natural scattered light (should be clear sky, partly cloudy northern natural light, and there should be no reflected light from colored objects around), compare the test plate with the corresponding color standard plate 
( or color difference plate) placed side by side so that the corresponding sides touch each other or overlap a certain area. When colorimetric, the distance from the eye to the sample is 500mm, so that the light is shot at an angle of 45° and observed at an angle of 0°, and the positions of the sample and the target are changed from time to time to improve the colorimetric accuracy. (2) Conducted under artificial sunlight The observation adopts a visual colorimetric box, and a D65 light source conforming to the CIE standard is used. When colorimetric, the light is incident at an angle of 0°, and the human eye observes at an angle of 45°, as shown in the figure below.
The result shows
If there is no significant difference between the color of the sample and the target plate, it is deemed to meet the technical tolerance range.
Reference standard
National standard GB/T 3181 "Paint Film Color Standard".
National standard GB/T 9761 "Visual color comparison of paints and varnishes".
