Foundry sand must preserve shapes in contact with a model and match all of its details. Metallurgical factories such as GHM in Sommevoire use several kinds of sands. Chemical setting sand consists of silica (for aluminum and cast iron), resin (1 to 2% of the sand's mass), and a catalyst (5 to 60% of the resin's mass). The catalyst helps to ensure cohesion between the grains of sand. The addition of resin and the catalyst is done just before molding by the metallurgists.