The foundry is built

Project of the week is making a firebox suitable for a foundry that can be used to cast brass, bronze, or aluminium. .. and with a bit of elbow grease, the foundry has been built.

A refractory lining made of equal measures plaster of paris and sand has been used to line a 12 litre galvanised steel bucket.

The process is reasonably simple, although I'd recommend thinking twice and acting once in most cases as having to think and act at the same time can prove difficult.  I'd mostly planned the build and it went mostly to plan so I'm considering this a success.

Having not mixed plaster by hand before I will confess some initial concern that I'd make a lumpy mess that wouldn't be a smooth mix by the time it started to harden, but within 5-10 minutes it was smooth enough that I couldn't feel any lumps with my fingers and I decided it was time to pour.

The centre space for the fire was formed easily enough and with only a little fuss and bother, and the mix solidified up reasonably quickly once its fifteen to twenty minutes was up so all in all the timing was pretty good.

The finished product, or about as finished as it'll get tonight.  My reservation is that I should have made more lining material so that the firebox is deeper. I'd want it higher up the sides and deeper on the base.

The measurements looked good on paper, and I did a test run with water to work out how many measuring buckets of water fill the steel bucket. So I expected the volume of the lining to be spot on, but the drymix doesn't pack like water and the overall mix was about 30% smaller that I'd expected. The lesson learned, of course, is that I can afford to mix too much and tip some away but not having enough is a bit of a pain.

The firebox looks large enough to get a good charcoal burn and well big enough to work on small projects like tools or knives.

The mix stays butter soft for a long time, and I was in too much of a hurry to get the holesaw out and get the blast hole cut. Next time - if there is a next time - I'll be happy to wait a half hour or so before cutting. The steel is pretty thin and offers little resistance, and while you want to cut the mix quickly I didn't have to put myself in a rush to do it.

More news as it breaks, but with the bank holiday approaching I should be able to fire this up and see how it performs.