Friday was the last day of another class I took at the Bullseye Glass Factory with Bonnie Celeste, entitled Design For Drop Out Molds. In this class, we were working with various sizes and shapes of drop out rings. Drop out rings are a mold that is a fairly flat surface with a hole in the center. When you place a sheet of glass on the mold and heat it to slumping temperatures, the glass falls through the hole in the center to make a three dimensional shape. Commercial drop out rings come in circles, ovals, and squares, and you can also make your own custom shapes out of fiber board. The photo to the left shows one of our projects still cooling down in the kiln after their slump firing.
Once again, Bonnie did a great job of choosing a variety of things in order to get us lots of experience within a short period of time. It takes about a full 24 hours for a full fuse firing, then almost another 30 hours for the slump firing, and we only had a total of three days of class. Since we would still need to do cold working on the projects after they were fused and slumped, Bonnie created two projects in advance that she pre-fused for us.
On the first day of class, we chose the glass that we wanted to use from her pre-fused projects and put them in the kiln for their slump firing. We also created another two projects from scrap glass in the class bins, along with frit (crushed glass) and/or stringer (threads of glass) that would be ready for cold working on the morning of our last day of class and got those in the kilns for their full fuse firing. The photo on the right shows one of our constructed projects cooling in the kiln after the full fuse firing.
We also talked quite a bit about where the project will stretch most during the slump firing versus where the glass will stay mostly intact. As it turns out, most of the stretch occurs right under the rim of the mold and the glass directly in the center of the ring is hardly distorted at all, since it basically falls almost straight down to the kiln shelf. That seemed pretty counter-intuitive to me prior to seeing the class samples, as it seemed as though the most stretch would occur at the lowest point on the piece, since it would need to stretch in order to reach the kiln shelf. If you look at the photo on the left up above, though, you can see how much the straight lines in the glass of the project closest to the camera widen out as well curve into a gentle arc from the slump firing, while the lines at the center of the piece still look very straight.
On the second day, we put the new fused pieces into the kiln for their slump firing and spent the rest of the day cold working one of the pre-fused projects. In the cold working part of the class, we learned how to use a wet tile saw to cut the rims off of our drop out pieces. Once the rim was cut off on the tile saw, we were left with a fairly nasty looking rim on our pieces, so we used a flat lap grinder, a wet belt sander, and loose grits with diamond pads to clean up the rims of our drop out projects. That was actually the most time intensive part of the class. Working from coarser to finer grits in order to get a great finish on the glass requires slow, methodical progress. I will readily admit that using the power tools speeds up the process incredibly, although there is still wait time for the equipment when there are multiple students all wanting to use the same tools. However, the end result is definitely worth the work.
The photo on the left shows my completed projects, two still with their rims intact and two after cold working. I’m leaving the rim on the square bowl as is, so that one didn’t need any cold working. Once my project samples arrive here at home (I had Bullseye ship my samples back home for me, since they were too heavy to put in my luggage), I plan to try removing the rim on the large round project (furthest to the left in the photo) with my ring saw. No one in the class, students or instructors, had ever tried removing a rim from a drop out project with a ring saw, and since I have one, I thought I’d see what happens. I’ll do another blog post here about the removal after I get the rim off and the rest of the piece is cold worked.
The two smallest pieces, the green and the vanilla streaky projects, were the ones that were pre-fused by Bonnie prior to class. The square bowl was constructed from Purple Gold transparent glass and black and clear streaky glass. I laid the colored glass over a square of Opaline opaque glass and then added stringers in Medium Amber, French Vanilla, and Carnelian Red on top of the sheet glass.
The larger round project included two black and clear twistees that I made during the previous class with Bonnie on torch working, as well as clear and Turquoise stringers in a grid pattern. It was made from a 10″ bottom circle of clear glass, which I sprinkled with Turquoise transparent powdered frit and swished around with a fan brush. Then I laid a matching circle of French Vanilla opalescent glass on top of the clear glass, and laid the stringers and twistees on top of the French Vanilla circle of glass. The reason why the Turquoise frit and stringers don’t look blue in the project after firing is that the sulfur in the French Vanilla glass interacts with the copper in the Turquoise glass to make a reaction that causes that brownish color.
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