The production of richly colored, fade-resistant exterior bricks primarily depends on the raw material used – clay. Currently, the clay used for exterior brick production falls into three categories: sand, regular clay, and colored clay. Bricks made from sand and regular clay are cost-effective but are limited to producing red, brown, and yellow colors. The color of the bricks varies depending on the region due to differences in the clay's natural color. To produce bricks in other colors, chemical dyes or glazes must be added. These additives have a significant environmental impact and result in secondary pollution in the production workshop. They also have adverse effects on the health of workshop employees. Bricks that use dyes or glazes tend to fade gradually over 10 or more years, especially under the strong ultraviolet radiation in New Zealand.
