BronzeWork

Sandcasting - how it is done

Casting of artefacts such as arrowheads was originally done by pouring metal into open moulds, a process not unlike making ice cubes in trays. While the techniques may have advanced some, the idea remains the same, ie to pour molten metal into a shaped hole. In its simplest form it goes as follows:

You start with a pattern (a) which is the same shape as the required article, allowing for the shrinkage of the metal as it cools and the amount of material to be removed in the process of finishing it.

A frame – the mould box – is filled with sand (b). The pattern is then put into the sand which is then compacted (c). Then the pattern is extracted from the sand, leaving the shaped hole into which the metal is to be poured (d).

To form the other half of the mould, sand is compacted into another mould box, and channels to allow the metal to enter, and the air to exit, are formed, referred to as runners and risers respectively (e).

The mould is then closed and molten metal poured into the hole. This is the exciting bit (f).

Once everything cools down, the mould is knocked apart revealing the metal article with the runners still attached (g). These are trimmed (“fettled”) and the item is then ready for the next process (h). 

The photos above show the mould being closed, and then the metal being poured during a casting demonstration at a maritime festival.