When making fused glass, the artist places the glass over a mould and heats it until the glass becomes malleable and drapes over the mould. This kind of mould is called a slump mould. You can make your own slump mould out of ordinary clay, using household objects to create impressions in it. The heated glass will "slump" into the impression and take on its features.
Knead the clay thoroughly, as though it were dough. Use the base of your palms and press them across the surface of the clay. Fold the clay in half and repeat the kneading process. Do this for 1 minute.
Rotate the clay by 45 degrees and knead it again for 1 minute. Kneading clay gets rid of air bubbles that could cause the clay to explode in the kiln.
Roll out the clay into a ball. Shape the ball into whatever shape you wish your mould to take. Select a household object to use as a model for your mould. Your object could be a figurine, a charm or anything else that catches your fancy.
Press the object into the clay. Be sure to press it straight down. If you do it at an angle, your impression may appear smeared. Gently pry the object out from the clay.
Allow the clay mould to dry out until it is bone dry. This can take anywhere from 1 to 1 1/2 weeks. Bone dry clay appears much paler than wet clay and has a glassy ring to it when you tap it with a fingernail.
Find a local artist studio that can fire your mould for you. Have the mould fired only once, as bisque ware is all you need for a slump mould. Fine art pottery, on the other hand, is often fired twice. Your mould will be 10 to 20 per cent smaller once it is fired.
Coat your mould in several layers of kiln wash. Kiln wash may be either sprayed or brushed on, depending on what kind you get. It will help to prevent the glass from sticking to your mould. Your mould is now ready to use.