1. What is a dye, and how is it different from a pigment?
A dye is an organic substance that allows fibers or other materials to be colored fairly firmly. Its chemical composition is complex, most of which are derivatives of aromatic compounds. According to the application method, it is generally divided into acid dyes, basic dyes, direct dyes, mordant dyes, vat dyes, sulfur dyes, reactive dyes, etc. There are many types and different uses.
Dyes are different from pigments. Dyes have bright colors and can be dissolved in water, ethanol, acrylic acid and other organic solvents, etc., and can make all the dyed objects colored; while pigments are insoluble in the medium, and can only color the surface of the objects. For example, dyeing wood with a dye solution, the solution can penetrate into the wood and undergo complex physical and chemical reactions with wood components (cellulose, etc.), so that the wood is colored without covering the wood grain.
There are two types of dyes commonly used in paints: acid dyes and basic dyes. The coloring power of acid dyes is generally weak and the color is light; the coloring power of basic dyes is strong, and the color is thick and bright at the same time.
2. What should I do if I can't tell whether it is a pigment or a dye?
There are many types of pigments and dyes, and their appearance, hue, and use are different. Only by being fully familiar with them can they be used correctly.
Examples of methods for identifying pigments and dyes are as follows:
(1) Determine the names of pigments or dyes by visual methods according to their appearance and hue characteristics. For example: carbon black and iron black, carbon black is pure black, while iron black is black with some reddish and so on. Another example is diamond yellow and iron yellow, chrome yellow is yellow with blue, and iron yellow is yellow with green black or red black; black sodium powder is purple red, yellow sodium powder is red with yellow, etc.
(2) According to the properties of the coloring substances, use tools to distinguish pigments or dyes. At the construction site, fingers or wooden sticks can be used to rub a small amount of pigment or dye with water to see its solubility or hiding power. Pigments are insoluble in water or oil, and have strong hiding power. Dyes, on the other hand, are transparent, colored substances that are soluble in water. Such as Responsible Powder and Haba Powder, in appearance, sometimes it is not clear, you can use boiled water to soak them in glasses respectively, after stirring, you can see that Huang Na Powder can be dissolved in water, and it is a transparent aqueous solution, basically without precipitation. and haba powder cannot be dissolved in water, and it is in the form of a turbid mixture, which will settle down after a period of time.
