Sunday, 15 June 2014

Lost Wax Casting

Learning new stuff is one of my favourite things to do. I have been taking a course in silversmithing at Sheffield College to try a few of the things I can easily do (Yet!) in my home studio, such as casting.

Lost wax casting simplified is basically to carve a design in wax. Make an investment mould around the wax - a bit like plaster of paris. Then stick the mould in the kiln to burn away the was - hence the lost wax. That leaves you with a mould to pour your molten metal into.

Turns out you can actually cheat - you can use any item that burns away in the kiln instead of wax, so what I did is use some of my growing collection of dried pods and fir cones.

They have to be attached to a tree of wax called a sprue - this is the channel that the metal will flow into. Here's my first attempt.

Once the pods and wax was burned away in the kiln I was ready for the centrifugal casting machine!
Once the lid is closed the little arm inside with the balancing rod will spin around really fast forcing the metal into every corner of the mould.

 The silver was added to the white crucible and heated up till it was a round shiny ball. Time to slam the lid.

Once the silver has cooled a little the mould is grabbed with tongs and plunged into a bucket where all the investment starts to dissolve and you can fish around for your lump of silver in there.

This is what it looked like fresh out of the bucket. There is still gooey investment stuck to it and the silver is black from firescale and oxidation. I removed the goo and plunged it in the acid bath to clean the scale off.

It took a few goes, but eventually it came out looking like this:

It then has to be tumble polished to reveal the shiny silver:

Now I just have to figure out what to do with all my lovely little pods. I think the poppy seeds are destined to be tiny necklaces - they don't match in size for earrings. The conifer cones on the other hand are perfect for earrings. Tiny little dangles.