At the beginning of 2019 I had the opportunity to explore glass casting. I began in a small dental kiln with a 3" x 3" x 3" fire box. Working with such a small kiln kept my experiments small and fire times relatively short. It also had the interesting constraint of only having one temperature, so I was able to focus on processes that didn't involve temperature, such as the moisture content of molds, mold recipes, and fire time.

At the beginning of this exploration I procured a microwave to use specifically for removing wax from molds. Working with investment molds, I found that removing the wax was most successfully done while the molds were damp. The moisture in the mold material turned to steam when heated in the microwave, and was very effective at removing wax. If I let the investment dry out before removing the wax, heating in the microwave was not effective at all. The investment material did not get hot in the microwave at all. Neither did the wax get hot enough to melt out. The presence of water in the mold material is essential for quickly removing wax from investment molds.

Another lesson regarding moisture - a wet mold going into the kiln releases more bubbles into the glass during casting. This may or may not be desired, depending on the piece.

The majority of my investment molds were a mixture of plaster and silica. I was able to get the best surface texture with recipes that contained a 1:1 ratio of plaster to silica. With small molds, I was also able to cast in molds made of 100% plaster (purchased at Home Depot). This is likely because my molds were tiny and my ramp time to casting temperature was short, which exposed the mold material to minimal high heat. I also tried recipes that contained 1:1:1 parts ludo/plaster/silica. These mold were also successful, but the texture on the surfaces agains the mold material were rougher than the 1:1 plaster/silica molds.

Next I am going to experiment with mold recipes that incorporate diatomaceous earth, in place of silica. I'm going to start with small mold experiments before moving to a larger kiln.

Almost all of the glass I cast so far has been 90 COE. I tried one experiment with recycling glass from jars, all from the same jam I buy at the grocery store. You can see the outcome above on the very left. The glass from the recycled jars did not have sufficient time to melt compared to the 90 COE glass house picture beside it. They were both fired at the same time, in the same kiln (a kiln larger than the dental kiln).

Colors: One of the most interesting parts of this exploration was casting different color glass in the same mold. I am fascinated in how the colors move depending on the amount of time the molds are kept in the kiln.

During this exploration I really began to internalize the value of working in multiples. I created a few silicon molds that I could easily pour waxes into. It was an invaluable process for working quickly and consistently to see how the experimental factor I was tweaking changed the final pieces. I was able to more effectively compare results casting the same shapes.

The piece in the above video was very interesting. I took one of the abstracted moth forms I had been casting and fired it a second time. The result was a slumping of the high points and a cracking of the surface texture created by the initial investment mold. The result is a really fascinating crackle texture.

How much detail is too much detail? This is another aspect of casting glass I am curious about. I cast a number of bunnies in various colors, all from 90 COE glass. I was very interested to see how the amount of time in the kiln effected to the level of detail captured from the mold and the texture of the glass. Curiously the pink/blue/purple bunny in the middle image above, ended up with the smoothest surface texture of all of the cast bunnies. I only had the kiln heating actively for 2.5 hours for this cast. As you can see, that was not enough time for the glass to flow into the very tip of one of his ears.

Exploring cast glass from Jan-April of this year, I have learned a great deal. I feel I now have a basic understanding of the process of casting glass and variables I can control to get particular effects. I also learned I'm very interested in continuing my work with this material.