Shoe Casting (with three-part retrievable mould)
The following details step by step the casting of a shoe, starting with a retrievable mould. The retrievable mould is made from three parts, when complete it will be used to pour wax into. The mould is designed to come apart so that the wax shoe can be cleaned up and invested in plaster, and easily made again, if desired. Firing schedules are included below.
1) Begin with the object you intend to cast, in this case a shoe, and draw lines on it depending on high points and undercuts, these lines will be where the different pieces of the mould meet.
2) The 1st of the 3 part mould process is to fill the shoe with a clay ‘foot' surround it with clay and sit it so that the dotted line is as horizontal as possible. Cover the shoe with a release (like petroleum jelly or clay slip) and pour the plaster. Wear a respirator while mixing plaster.
3) Flip over, do not remove the shoe or the plaster, make a dam around the heel - but only up to the flat surface on the inside. Cover shoe and exposed plaster with a release and pour plaster. Wear a respirator.
4) Take the dam away from the heel, cover shoe and exposed plaster with a release, pour plaster. Wear a respirator. Once plaster has set, open the mould, clean, and soak in water, make it touch dry.
5) Heat wax (I have used ‘Techniwax) until it is all melted, remove from heat and let it sit for a few minutes. Ladle or pour into mould (which is tied up with a rubber ribbon to secure it) swoosh it around inside the mould and pour out in a smooth motion. Let sit for 20-30 seconds and repeat, continue to repeat until desired thickness is achieved. Let set overnight. Always wear safety goggles and gloved when using hot wax.
6) Trim and tidy the wax shoe using the appropriate tools.
7) Attach a large wax cone revivor – this can be quite difficult. You can use a soldering gun or a paintbrush, dipping it in hot wax, to help solidify the join. Be patient. WEIGH THE WAX (including shoe and reservoir). Wear safety goggles.
8) Investing the wax. ALWAYS WEAR A RESPIRATOR WHEN USING SILICA. Stick a toothpick coming straight out of the heel so air can escape.
a) The first layer is made up of equal parts of water, plaster and silica, and usually a handful of talc, splatter this layer on so as to minimise air bubbles.
b)The second layer is made up of equal parts of water, plaster and silica. Make an even layer over the first.
c) The third layer is made of equal parts of water, plaster, silica and grog or brick dust. Flip it over so that the ‘heel' of the shoe
would be on your work surface, and build up a large and sturdy base – this is an awkward shape that needs support to stand up in the kiln.
9)Calculate how much glass you will need, and add a little extra for good measure. Set up inside the kiln on kiln shelf, with pieces of kiln prop laying over the opening and set up a terracotta flowerpot with the glass in it on top.
Ramp to Temp Hold
Stage 1: 030*p/hr 200* 2:00
Stage 2: 050* 600* 2:00
Stage 3: OFF 850* 8:00
Stage 4: OFF 440* 1:30
Stage 5: 007* 360* OFF
Stage 6: 015* 310* OFF
Stage 7: 075* 24* OFF
10) When casting is over, wearing safety goggles, and a respirator, carefully break away mould material. Be wary or scratching the glass with tools you might use to assist in removing the mould, and also of shards of glass.
11) Finally, cut off reservoir and cold work your shoe to desired finish.
Jennifer Collins - 2005