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most important metal for enamelling is iron, both cast and sheet. Cast iron is used for baths, steam- jacketed pans, and the like, and sheet iron for cooking utensils, advertisement signs, etc. CERAMIC CHEMISTRY. 53 The best compositions for these are : CU^pf f A p,] Sulphur . . 04-0 05 Phosphorus 0.03-0.09 1.0- 1.8 Silicon .01 2.0 0.04-0.06 0.5-0.7 Carbon . . 10 3.5 But Griinwald gives the manganese for sheet metal as 0.23-0.35 per cent. The metal, before enamelling, must be pickled or sand- blasted. An enamel on metal must fuse between 850-1000 C. It must mature in a few minutes and be fluid enough to lie evenly. It must withstand sudden changes of tempera-