The moire designates the fabric obtained by the mechanical process invented by the Lyon manufacturer Tignat in 1843. This process consists of a partial crushing of the fabric by calendering by folding the fabric on itself. The weft then deviates, and, losing its original shape, offers to the light new reflective surfaces, alternating waves and matt and shiny stripes. It also designates by extension the visual effect (moiré) similar to the one caused by this textile (changing brightness, wavy and shimmering appearance). Scum: 1. whitish foam that forms on the surface of agitated, heated or fermenting liquids. 2. impurities, slag that floats on the surface of molten metals.