The madder dyestuff is combined with a dye mordant. According to which mordant used, the resulting color may be anywhere from pink through purple to dark brown. In the 18th century the most valued color was a bright red known as "Turkey Red". The combination of mordants and overall technique used to obtain the Turkey Red originated in the Middle East or Turkey (hence the name). It was a complex and multi-step technique in its Middle Eastern formulation, some parts of which were unnecessary. The process was simplified in late 18th-century Europe. By 1804, a dye maker George Field in Britain had refined a technique to make "lake" madder by treating it with alum, and an alkali, that converts the water-soluble madder extract into a solid, insoluble pigment. This resulting "madder lake" has a longer-lasting color, and can be used more efficaciously, for example by blending it into a paint. Over the following years, it was found that other metal salts, including those containing iron, tin, and chromium, could be used in place of alum to give madder-based pigments of various other colors. This general method of preparing lakes has been known for centuries but was simplified in the late 18th and early 19th centuries.