I've been very fortunate to be able to take glass classes at OSU. This semester I took an intermediate level course where I learned how to incorporate imagery in fused glass and mold making for glass casting. I used an old demo bowl that has traveled with me for years to learn how to make a two-part rubber and plaster mold. What a fun adventure! The mold I made can also be used for bronze casting, and I was given an opportunity to participate in this semester's bronze pour at the Sherman Center for Art.
Kudos to Becca Arday, my instructor for the semester. She did a fantastic job of explaining each step of the process. Just to give you an idea of what it takes to make a mold for casting I'll outline the steps.
Use plasticine to secure the object of interest in a custom-made frame for pouring the first part of the mold. Add a transition for pouring in the wax.
Mix a two-part rubber epoxy and coat the object until it is 1/4 inch thick throughout the mold. This involves about half an hour of pushing the rubber around as it thickens.
Add registration keys to the semi-solid rubber. Let the rubber set for about 24 hours.
Add a thick layer of plaster on top of the first part of the rubber mold. Let it set for 24 hours.
Remove the first part of the mold from its frame, clean up the mess, and start the second part of the mold by repeating steps 1-4.
After the two-part mold is made, condition the mold in water to thoroughly wet the dried plaster. Wrap the mold in strapping tape to keep the two halves together.
Use melted wax and pour into the the mold. Watch the cooling process and pour out the wax after a rim is formed. The wax casting is hollow.
Let the wax cool completely before taking apart the mold. Clean up any flaws.
Use another plaster mold for making a reservoir that will contain the glass to be melted. Once this has cooled the two wax castings are joined together.
The resulting wax cast is used for making another two-part mold consisting of plaster and silica for the first layer and plaster, silica, and grog for the second layer. The top of this mold is leveled for eventual placement in the kiln.
Steam out the wax and clean the interior of the mold with boiling water.
Measure the volume of the mold to calculate the amount of glass (by weight) that will be added.
Dry the mold completely (in an old kiln).
Clean the glass pieces and weigh them to the measurement calculated.
Take the mold to the kiln. Settle it on a small pile of sand and make it level. Add the glass.
Run the kiln for the length of time needed to melt the glass and anneal it.
Break off the mold from the glass.
Separate the reservoir from the object and clean up the glass to the desired finish.
The process takes about two weeks altogether. Once a mold is made, though, it can be used until it wears out.
The bronze casting mold is a different process, but I've already made this post too long. At any rate, I had a blast learning a new technique and I want to continue this series.