There are a number of variables that can effect a glaze’s color. These mainly fall within a group of three major factors.
- The composition of the glaze. This not only includes the colorants in the glaze, but also other glaze materials that i
nteract and effect that colorant or combination of colorants. - The temperature to which the glaze is fired. Some colorants are volatile and will dissipate into the kiln atmosphere if fired too high. Others give different colors at different temperatures.
- The kiln’s atmosphere during firing and, in some cases, during cooling.
Source: https://www.thespruce.com/ceramic-and-glaze-colorants-2745859