For very delicate work, loam, which is a clayey sand mixed with ordinary sand, must be used. The mould can be made in the ordinary way, but it must be well dried on both sides if double-faced work is to be done; for single-faced work only oue side will need well drying. When the mould is thoroughly dry, its faces must be smoked by means of a torch made from pitch. This deposits over each part a surface of finely divided soot. The pattern must then be inserted and the two halves of the mould brought together and screwed up, which will bring out the impression of the pattern sharp and clear. If loam is used for making the moulds, it should be mixed with facing sand. For small castings, charcoal powder mixed with about one-eighth of its volume of fine sand may be used, or the mould may be dusted with pea-flour and finally with charcoal. In moulding the thin parts of a delicate pattern, the mould must not be rammed too hard, as the metal, on cooling, will contract; if the mould will not give way, the metal must do so, and consequently there will be flaws or cracks in the casting.

This may be prevented by slightly damping the thin part of the mould with charcoal and water.

In making moulds fin-fine brasswork, ordinary sand should be mixed with loam, which is a more clayey sand. The mould must be well dried before a fire, and then dusted with very tine charcoal powder. If a very delicate surface is desired, it could be smoked over with a pitch torch. This method is more troublesome, but the results are excellent. The patterns must be inserted after the smoking, and the two faces brought together again. The soot from the smoking will give a perfectly smooth surface, and the castings will come out clear and sharp.