The past few days I've been attending a class taught by Michael Dupille on Glass Mold Making for Kiln Casting. I've been doing art glass work, ranging from mosaics, stained glass, hot glass beads, and kiln work, for the past few years, but this was my first experience making molds. Unfortunately, I don't have as much time as I'd like for my glass work. I also don't have a dedicated place set up to work. This is particularly a problem with bead making, which requires an open flame from a hot-head torch. I don't really have a place to be running an open flame!
Classes with Michael are always informative and fun. Last year I took his Fritography class which focuses on making glass projects from frit. (Frit is crushed glass available in powder, fine (like table salt or sand), medium, and course (roughly .25 inch or centimeter chunks) sizes. The easiest way to describe Fritography is compare it to sand drawings. Only, you use glass and fire the project in a kiln--repeating the process several times to get the final product. This picture is the corner of one of my projects before it's second firing (in other words, I built the project once with frit, fired it in the kiln, and then re-built it adding texture and color for a second firing). Click on the picture to see a slightly bigger image. This piece has cut glass (the white and black tree trunks) and three sizes of frit: powder, fine, and medium.
This year's class, held at United Art Glass in Naperville, Ill., was on Mold Making for Kiln Casting. Unlike last year, where I tried to make two fairly complex projects for a beginner, this time I decided to make very simple projects and focus on learning the processes. In case this doesn't interest you, I've put pictures and explained the basic process in the extended entry, which is linked below.
The first step to forming glass in molds is to build a model. Again, I was going for easy, so I shaped a star with a sun on it. The model is made of clay or Plasticine. Then a dam is built around the model. Here we cut a strip of cardboard as the dam, wrapped it around the model, and lined the base of the dam with more clay--both on the inside and outside to prevent the mold solution from leaking. There's also a wire poking out of the highest point of the model to create an air hole in the mold.
Next, a molding solution is poured over the model. We used Castalot, a molding solution for kiln firing that Michael developed. Most molds can only be used once in a kiln, but Castalot can be used more than once--a great time saver. Below Michael is pouring Castalot. Notice the model he is pouring over has several wires, instead of one like mine did. That's because the model had several high points and needed more air holes.
After the mold sets for 40 minutes, it is separated from the model. I chose to make additional carvings in the mold, see the sun beams in the image below that the clay model didn't have. Then the mold is pre-fired to remove moisture and for it to completely harden.
Now it's glass time! The mold is coated with kiln release so the glass doesn't stick and then glass frit is put in the mold. Once the colored frit is added, a mountain of clear frit is added for thickness to the bottom of the mold (but I don't have a picture of mine coated with the clear). Then it goes into the kiln and fired in stages to over 1300 degrees.
And here's the final product...well, not completely final...I need to grind the roughness on the bottom edges to smooth them out. I'm glad I went with a simple design, but wish I'd added more blue frit to the edges so less clear glass was visible on the sides. If I'd had more time, I would have added a moon in the bottom in the clear glass. ;-)
Before the clay in the first image above is messed up, a second mold is made with a different, non-kiln firing solution. From that second mold a polyurethane model is made. This is because the original Castalot firing mold can be used more than once, but will eventually wear down and the polyurethane can be used to make more firing molds.
We also made two other types of molds. One was a shell mold which is basically the steps above, but without the dam. Lastly, we etched a pattern into em-board to create a bas relief mold. A great, fun class that I'm glad I took! Now, I just need to get a kiln so I can start making these at home and get better!
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