Casting Axes - Part 3
Delta resin with silica sand mold for a palstave.
This semester I began with a new mold material. Delta resin with silica sand and catalyst. This is a resin based medium that duplicates soft sandstone. It’s easily carved, even with wooden modeling tools and has a texture that is remarkably like sandstone. Unfortunately the resin breaks down at high temperatures and while it makes a great mold, it still is only good for one pour. On the plus side the carving goes quickly and I don’t have to wait for it to dry as I did with the clay molds. It didn’t take long to make molds for two axes and they were ready to cast with only a little preparation. To make a smoother surface I mixed graphite and zircon (50/50) and added enough denatured alcohol to make a thin solution. This was painted inside the mold and then lit to burn off the alcohol.
The molds did not require warming and after clamping they were ready to cast. This time I used a standard bronze of 90% Cu and 10% Sn. The pour went beautifully and the axes need very little finishing. I was able to break off most of the flashing with my fingers and used a grinder to take off the sprue. I had expected some shrinkage and so had made the molds slightly larger than the models. However, there was no shrinkage so I’ll have to allow for that for the next pouring. I now have a set of axes as soon as I can find some serviceable branches to make into hafts.
Notes: In order to estimate the amount of metal needed, sand is poured into the mold and then weighed. The weight of the sand x 5.3 = the amount of metal needed for casting.
References: Potratz, Wayne 2005 Hot Metal (Minneapolis: Turtle Sign Company)