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From time to time I do a spot of pewter casting, it’s something I got into when I was a kid and dust off now and then. I knew I was going to have a couple of days hanging around the house this week so I did a little project – make a slime mould pendant. The equipment is really basic, pewter melts around 200C so you can ( and I do ) melt and cast it on a stove. I like lost wax casting – with my crude equipment it doesn’t always work and that makes the ones that do seem more worthwhile.
I made a beeswax oatflake, painted it with oat slurry and left it in a slime dish overnight.
The lump at the bottom is both a handle and the sprue – the channel the metal gets poured through.
Dipped in a mix of plaster and chinchilla sand – the ‘sand’ is actually clay and makes the plaster more porous and less likely to crack when it’s heated, this batch started to set alarmingly fast, probably ‘cos I hadn’t cleaned the bucket since the last one.
Dried overnight in the airing cupboard, the mold goes onto a charcoal stove for an hour – the wax melts out and burns taking the fried corpse of the physarum with it ( you can do this in an oven but it fills the kitchen with greasy smoke ).
The casting rig – told you it was basic. The bike wheel is a centrifuge – if you attach a drill to it – spinning the mould draws the metal in with a bit more force, expelling gasses and getting more detail out of the mold. This is probably extremely dangerous but yes it really does work.
This is why we wear gloves and safety glasses – the can sprang a leak! The rushed pouring may have spoiled it all :o
Once it’s properly cool a swift clout with a rock breaks the mould apart – the clay helps here – straight plaster often needs swearing and a chisel.
Even better after a scrub
Getting the sprue off and drilling a hole takes a couple of minutes. I like my pewter to have a dark tint so I need to patinate it – I use silver nitrate which quickly turns the surface black ( and anything else it touches ). I use a wad of kitchen foil to polish – it only reaches the raised areas so produces a nice antiquish finish.
The mess up in pouring means I’ve lost a lot of detail – the bottom has some really fine features but the rapidly cooling metal didn’t fill in the rest of the mould very well. This one might end up back in the melting pot.
i hope it's not too hyperempathetic of me to hope you perfect it soon, for the sake of all the poor slimes you keep frying...
They actually survive embedding in plaster - I've had them ooze out of moulds before and go for a wander, of course if you bake them at 200 c for and hour the situation changes.....