Only garments made entirely of polyester, such as the Gildan Performance (r) 42000 and 42400 T-shirt families, are acceptable for dye sublimation. These shirts were designed for high-volume production and should be used with care. They may not retain their color as well as other products that are not polyester. Shirts made from cotton may fade when exposed to heat or chemicals. If this happens, they should be washed in cold water and then dried flat to preserve the colors. Cotton is a natural product that will undergo changes when subjected to prolonged exposure to heat or chemicals. This can happen during dyeing or printing processes or because cotton fibers are susceptible to bacteria and fungi which can grow under certain conditions. This could lead to colors fading or clothes losing their shape. There are two types of dyestuffs used in textile manufacturing: direct and reactive. Direct dyes are those that require no previous treatment of the fiber, while reactive dyes need to be applied to the fiber after it has been scoured. Both types of dyes can be dissolved in solvents and then applied to the fabric. The solvent is allowed to evaporate, leaving only the dye in the cloth. Most dyes are both soluble and volatile so they can be used in either type of process.