Four years ago at Kentwell Hall I spent ages trying to make a stone mould for casting spoons in. It failed in a somewhat spectacular manner – I accidentally carved one side of the mould at the wrong angle, so the pewter ran out the bottom. An understanding of the shape required to make a spoon should make it clear why this would happen. Here are the two parts, on the left the male, the right the female with the indent for the bowl of the spoon. The male side has to fill the bowl, whilst leaving enough space for the metal to run between both sides. But I couldn’t see how to get both sides to match up perfectly when I was carving, and the result was as said. The white stuff in the photos is plaster, put there to try and block up the gap, but it didn’t work. This view from end on should make it clearer, the white plaster being on the right hand side: You can see that the metal enters from the top of the bowl, and there are clear grooves cut to allow air out of the mould.
What I have just realised now, a few years too late, is that looking at the medieval stone mould pictured in this book:
, the bowl is sunk somewhat into the stone, i.e. the rim of the spoon is below the level of the upper face of the mould. This will firstly help give a good seal when the two parts are pressed together, and secondly might also allow room for manouvre in carving the bowl. Of course without the other half it is harder to be certain, but I think that indenting the female part and raising the male part above the level of the joining plane would perhaps make carving it a little easier. Ahh well. At least there is enough stone to spare that I can try to remake the mould and this time make a better job of it.