We grind the gypsum with the pigment

To color pigment evenly distributed and mixed with gypsum, it should be rubbed for a long time. It took me about 4 hours. The pigment, although it is in the state of a powder, but from time to time is lost in grains, like a manga. These grains need to be grinded together with gypsum. In this case, we will get an even and uniform color of the future product. I used a black pigment in an amount of 4% of the amount of gypsum by weight.