MONGRAMS, SIGNATURES & DATES / FOUNDRY MARKS >
WEIGHING WAXES
Useful data that can be obtained by the founder from a given wax pattern includes an indication of the likely weight of the finished cast. This information can be useful for calculating the amount of metal required for the CHARGE, also estimating in advance likely weights for freight costs and so on.
Realistically, it is not possible to accurately weigh a cored wax pattern, unless a careful record has been kept of the quantity of wax in the slush, or else plaster, grog and water used in the mix (including an evaporation allowance). Weighing waxes is a more common practice in ceramic shell foundries that use an ‘open core’ investment system. Wax patterns for this process do not contain a solid core mass and can usually be easily and accurately weighed on scales.
The likely weight of a metal cast can be calculated by multiplying the weight of the wax pattern by a known factor. The factor of multiplication varies according to the alloy selected for the cast. Taking the example of a common copper alloy (BRONZE, BRASS or GUNMETAL), the round multiplication factor applied is X 10. Therefore a wax weighed at 1lb will produce a bronze cast in the region of 10lbs. ALUMINIUM casts are approximately one third of the weight of equivalent copper alloy casts, and so the multiplication factor is adjusted accordingly (wax X 3).
To correctly calculate the amount of alloy required for the molten charge, the founder must also allow for the volume of metal taken up by attached RUNNERS, RISERS and POURING CUP. Most experienced art founders are able to estimate the quantities of metal required for a given pour by experience rather than outright calculation. The founder will additionally allow a safety margin when determining how much metal to use, and so minimise the risk of SHORT RUNNING the mould.
PREPARING A WAX PATTERN FOR INVESTMENT >
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