Knowledge of Ceramic Colors

Introduction of Ceramic colors
Ceramic colors is a generic term of all pigment used on ceramic, including over glazed pigment, under glazed pigment, glaze and body coloring pigment.
Different Requirements to Ceramic Colors of Different Usage
In the ceramic production process, these pigments are subjected to the calcination of different temperatures. There are different requirements to ceramic colors of different usage. Under glazed pigment has to be clacined under high temperature (1300 ℃), which requires high stability. However it is divided into less variety. The earliest under glazed colors are the blue and white, underglazed red, and in recent years red, yellow, blue, green, black, gray, and brown have been made. Overglazed pigment only needs to withstand a temperature of 600 ~ 800 ℃, and thus it can be divided into a wide variety of rich colors. In addition, liquid pigment is used as a glaze polychrome, such as Goldwater, etc. It is combined into vulcanization ointment by metal and organic matter, coupled with organic solvents. In the seventies, it developed into a high temperature fast burning pigments (in-glaze decoration). The decoration firing temperature is 1100 to 1260 ℃, and the decoration firing time is 35 to 120 minutes.

Preparation Process of Ceramic Colors
Mixing
The final hue of the colorant is largely influenced by other ingredients added to the colorant. Accordingly, in order to make sure each batch of pigment is in the same hue, raw material of the same quality must be carefully weighed and mixed in accordance with the composition. Calcination
Calcination is an important step of the ceramic colors manufacture, and its purpose is to make the colorant stabilized. During the calcination process, due to the difference of nature of raw materials and pigment hope to get, the reaction will be different. The lowest calcination’s temperature should be the same as the final pigment products’.

Washing
Pulverize the ceramic colors after calcination, and then in order to clean out all the soluble substances, pigments should be washed with water. Pigment using chromate must be washed with hot water. If there is remaining soluble chromate, around the chrome there will appear uneven colors. If you do not clean out borate, there will appear thin film on the pigment.

Pulverization
After washing, the ceramic glazes should be pulverized to the desired fineness with pan mill or a ball mill by waterproof pulverization method. Although there are no express terms of the particle size of pigment, the general requirements are that all the pigments can pass 300 mesh sieves. When the pigment is not pulverized enough, it will be hard to use because of uneven particle, and will turn into mottling after burning because of shortage of covering power. Conversely, if pulverize the pigment excessive fine as dust, it will not sufficiently fuse in the glaze but occur roll glaze.

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