Lost Wax Casting - Continued

lostwax2_2.JPGOn the previous page, I prepared my lost wax mould for casting pewter - so now it's casting time!

lostwax2_1.JPGI wrapped the mould again in duct tape, in case the heat of casting makes it burst. I also set it in a box of sand to contain any spillages and support it while I pour.

To prevent sand getting into the mould while setting up, I covered the top with plastic film - this will just burn away when I pour the metal.

lostwax2_2.JPGI put the can of pewter pieces on a gas camping stove on full heat

Before very long, the metal began to melt. When it was fully liquid, I picked it up with a long plumber's wrench and poured it into the waiting mould.

It poured quite cleanly, but then began to bubble quite fiercely for a while before settling down.

lostwax2_3.JPGI left it to cool for half an hour, then removed the tape covering.

The mould was still intact and felt very heavy, hopefully indicating a successful fill.

lostwax2_4.JPGI started to crack open the mould by tapping gently with a small hammer.

Pieces of the casting started to show - looking good so far.

lostwax2_5.JPGThe mould crumbled away quite easily, leaving one quite solid casting.

An initial inspection revealed one quite large void - a bit of a shame, but otherwise, the casting is in one piece, and is approximately the right shape.

lostwax2_6.JPGI scrubbed away the last few bits of clay, then cut off the sprue with a small hacksaw.

There were also a few little tags and blobs where there must have been bubbles or imperfections in the layer of clay immediately covering the wax - I cut these off with wire cutters.

I gently filed away any remaining sharp or protruding bits, and it was finished.

So here it is - it's not perfect, nor is it elegant, but it's almost exactly what I was aiming for, so I'm quite happy with it.

lostwax2_7.JPG

Lessons Learned

This was my first attempt at lost wax casting and as usual, I approached it without any particularly deep research on techniques and materials. It worked out pretty well, but there are some things I'll do differently next time.

Mould Material

I think the air-drying modelling clay I'm using is a mixture of mineral clay and some kind of glue - probably PVA. I don't think it dries completely enough to be used for this purpose - under the heat of the molten metal, it emits steam, which might create flaws or porosity in the finished cast piece.

Next time, I think I'll use ordinary potters clay.

Voids

lostwax2_8.JPGThe finished piece ended up with quite a large hole in it - caused either by trapped air during pouring, or escaping gases from the clay material

It's a shame this happened, but it's not enough of a problem to make me want to scrap and recast the piece - I was aiming for a primitive look anyway, so this isn't completely out of place.

'Tiny Shiny Horse' was almost immediately named and seized by my daughter - so now I have to make something else for my son - detailed on the next page...

Comments

1. On Wednesday, January 19, 2011, 23:36 by Jacko

There is some risk in giving a pewter toy to a small child, because of the lead and tin content. As a model figurine on the shelf they are wonderful, though.

2. On Saturday, February 21, 2015, 10:14 by Liz

Thereason for the void, I think, is gases being trapped when the metal pours in. I've seen this done before with large scale bronzes where thin tubes of wax are attached near the bottom to make air channels- these make long sprues that can easily be cu

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