Silico aluminate of sodium polysulfides. In 1828, the chemist Guillemet synthetically reproduced the natural colour of Lapis Lazuli, which had been in use since antiquity. Variations in the hue result from the size of its microparticles. The preparation of ultramarine blue is quite complex, and varies according to the desired individual shade. Luminous, intense blue that approaches the appearance of cobalt blue, and provides bright, pleasant effects in shading. Mixes well with other pigments, but, since it contains sulfur, should not be mixed with flake White or chrome based pigments. Suitable for all techniques.