A day of questionable brass, wet molds, short-supply of gas. These are the problems I need to rectify.
1. Preheating the plaster mold to minimise reaction with hot metal.
2&3. Pouring the brass. You can see the mold on the left reacted more, as it wasn't preheated.
4. You can see how the one on the right reacted badly, where as the one on the left filled in all the way. Unfortunately I don't think the brass is pure. I tried to scrape off a lot, but much of the brass was being lost in the process. I need to find pure and unquestionable brass.
5. Even after a quick wire brush you can see it needs doing again.
6. Another attempt. It filled in much smoother but the brass was too cool I think and stopped pouring half way through filling the mold. GRRRR!
7. Total failure again. Full of holes and pits, then the mold separated. Back to the drawing board.
The brass I am using is from old bolts and brass pipe and gas fittings. I am beginning to doubt how much of it is actually brass. I'll do some research on the right brass to be doing this with.
Oh well, better to have a go than procrastinate about doing it.