Matt's Intro to Glass Casting
These are photos of some of the pieces I made during a one-week intensive art class at Penland School of Crafts in glass casting, taught by Junichiro Baba, master glass artist from Japan. The photos were taken by my good friend, the talented and oh-so-charming Jon Silla. He succeeded in making my humble experiments look like true art. Keep in mind that this was my first exposure to working with glass in any form – all these pieces, plus more not shown were produced in less than one week and all were created as a means to learn the medium and various casting techniques. Ideally, I would have spent more time per piece… some I hope to recreate with more attention to detail. But overall, I'm pleased with my first attempts.

The first two images are of the very first set of pieces I produced. These were sand-cast, a technique where an impression is made into dampened sand (mixed with a small amount of Bentonite clay for formability) and then filled with molten glass scooped from the furnace and poured with a cast iron ladle. I used a textured kiln brick to create the impressions. Once the glass was annealed (heat-soaked to relieve it of stress) and cooled, the two bricks were cut on the diagonal using a diamond circular saw. Then the cut surfaces and bases of each piece were ground and polished smooth. Pretty elegant result, considering how simple the process was.

The piece in the following two images was also sand-cast following a technique demonstrated by Junichiro. I created a rough trough in the sand and poured a narrow strip of hot glass into it. When the glass began to cool (but while still pliable), I manipulated it by hand – wearing heavily insulated fireproof gloves, of course. A wooden stick helped in the sculpting process, although it was constantly set on fire from contact with the hot glass which is up to 2200° F. One must work quickly but delicately to create the manipulated form – once it sets into shape, it must be immediately loaded into the annealing kiln. The first piece I created this way actually broke as it was loaded because it had cooled too much.

The statuette was made using a kiln-casting method. The figure was first sculpted in clay, then plaster was poured over it and allowed to set to create a mold. The clay was then removed and the mold cleaned and prepared for firing. Cut glass (cullet, frit or powder) was measured and weighed to the amount needed, then filled into the mold. I used orange-tinted cullet (chunks) for this figure, which resulted in a high degree of transparency. Frit is a granulated consistency and results in more trapped air between the particles, creating a more opaque glass. This piece is still unfinished - the excess glass around the edges still needs to be ground off and the surfaces finished.

The last set of images show a series of sand-cast pieces I call my "Autumn Leaves" series. I learned from Junichiro that glass and copper share a similar thermal coefficient of expansion, meaning the materials can be safely combined together while hot — as they cool, the copper will not stress and crack the glass like other metals or materials might (at least in theory, there are many variable that come into play and nothing, I'm learning, is guaranteed when it comes to glass). The leaves are hand-cut and stamped from 24 mil sheet copper and are modeled after leaves gathered on Penland's campus. I used a wood block and kiln grate cut to size to create the textured casting molds. The casting process for each piece involved a 3-step process. First, a half inch or so of molten glass was poured into the mold. I had an assistant heating the copper leaf nearby with a blowtorch — the red-hot leaf was then positioned on top of the hot glass and another layer was immediately poured on top of it, encasing the copper leaf inside the glass. This process was repeated for each individual mold. Some of the pieces include trapped air pockets surrounding the edges and surfaces of the copper, an interesting if unintentional effect. I have noticed that one of the pieces (the maple leaf) has cracked internally in several places. Most of these cracks were not visible when the piece first came out of the kiln, so I assume that the stress was not relieved completely during the annealing process. Castings can sometimes devitrify, crack or explode months or even years after they are made, and it is usually due to a bad batch of glass or improper annealing — that's why precision is vital.

Note: You should be able to click on each image for a larger view but Blogger has big problems with images uploaded from Safari, and I do not use other browsers on my Mac. I will try to find a work-around, but If you want to see a larger view of anything, just email me.