Lately I have been having difficulty with casting a certain mould that in the past had no issues casting at all… It took me ages the other day to cast 4 of these tokens and even then, the 4 that I had cast were not the best quality. It took me a while to work out what exactly was causing the issue and when I did, it didn’t really help the situation.
The issue is that at the moment the humidity in Sydney is very high… This humidity seeps into the soapstone moulds, and normally just preheating the mould would be enough to expel this moisture and creat reasonable castings. However with the humidity so high, it’s seconds before that moisture is back… It’s in the mould instantly, as it’s in the air that is expelled when the molten metal is poured in. What it does to the casting process is cause miniture steam explosions which make bubbles in the cast metal. This is an issue that I’m at a loss to get around at the moment, other than picking nice low humidity days to do my casting.
There is a method of using steam as a means of pressure casting, however it still requires a warm dry mould to provide a decent casting. I have only heard this method talked about, and have yet to see it in action.
I’m trying to cast tokens for Midwinter Coronation. I think I’m having the same humidity problem with the mould. If I heat the pewter until it only just melts I have good detail but don’t get complete flow through the mould. If I heat it properly the detail is terrible and it looks like bubbles through the surface of the pewter. At this stage with only a week to go I think my only option will be a silicone mould.
Did you find any way to get the soapstone to behave in winter?
Cheers
Nathan Blacktower
Hi Nathan,
I did end up managing to get some reasonable pours but the way I did it was to heat up the mould and keep it hot. Basically I put the soapstone over the flame of my cooker for about 15 minutes on a low flame, making sure that there was a uniform heat through the mould. Then when I started pouring, I didn’t stop for any longer than to drop another ingot into the ladle. It’s also best to maintain a decent amount of molten pewter in the ladle so that when you drop in an ingot it melts quickly.
I ended up developing a rhythm and getting through the 20 or so tokens that I needed to do.