FOUNDERY of small works, or casting in sand. The sand used for casting small works is, at first, of a pretty soft, yellow ish, and clammy nature : but it being ne cessary to strew charcoal dust in the mould, it at length becomes of a quite black colour. This sand is worked over and over, on a board, with a roller and a sort of knife, being placed over a trough to receive it, after it is by these means sufficiently prepared.
This done, they take a wooden board, of a length and breadth proportional to the things to be cast, and putting a ledge round it, they fill it with sand, a little moistened, to make it duly cohere. Then they take either wood or metal models of what they intend to cast, and apply them so to the mould, and press them into the sand, as to leave their impression there. Along the middle of the mould is laid half a small brass cylinder, as the chief canal for the metal to run through, when melt ed, into the models or patterns; and from this chief canal are placedseveral others, which extend to each model or pattern placed in the frame. After this frame is finished they take out the patterns, by first loosening them all round, that the sand may not give Way.
Then they proceed to work the other part of the mould with the same patterns in just such another frame, only that it has pins, which, entering into holes that correspond to it in the other, make the two cavities of the pattern fall exactly on each other.
The frame thus moulded is carried to the melter, who, after extending the chief canal of the counterpart, and adding the cross canals to the several models in both, and strewing mill dust over them, dries them in a kind of oven for that purpose.
Both parts of the mould being dry, they are joined together by means of the pins ; and to prevent their giving way, by reason of the melted metal passing through the chief cylindrical canal, they are screwed or wedged up like a kind o f a press.
While the moulds are thus preparing, the metal is fusing in a crucible, of a size proportionate to the quantity of metal intended to be cast.
Some of these small work founders' furnaces are like a smith's forge, others stand a few feet under ground, for the more easily and safely taking out a weigh ty pot of metal ; which is done by means of a circular tongs, that grasps round the top of the crucible. When the metal is melted, the workman pours it through the chief canal of each mould, which con veys it to every distinct pattern.
When the moulds are cool, the frames are unscrewed, or unwedged, and the cast-work taken out of the sand, which sand is worked over again for other cast ings.