Five Finger #1: Stumpbowl

Home>glass>fusing>tack-fusing>Five Finger #1: Stumpbowl

stumpbowlcloseupI’m taking a brief hiatus from my pate de verre while I figure out where I’m going with color in my casting work. Sometimes when I get stuck, playing around with the glass helps me kickstart work in the problem area. So…I’m playing, and I’m trying to concentrate more on texture than color.

Hence Stumpbowl. I’m really fascinated by chunks of glass, and kinda sorry to see them melt down and become smooth and glossy in a flat work. Tack-fusing them so they retain the chunky, crystalline form and still hold together-that’s fun. Dunno if I’d ever try to do it with functional ware, but as long as I’m playing….

I started by chunking up some funky glass rods I picked up at the Bullseye Resource Center before the holidays. They’re called freaky streaky strikers, and they’re closer to millifiore than glass rod, with one or more colors in the core and a different color in the outer wrap.

stumpbowltackfusedI had a bunch of them in ambers and cremes, and I wondered what would happen if I tack-fused them to a base, then slumped it over a steel form to stretch and move the base glass. If I made them a bit oversized, the tops of the chunks should droop with gravity toward the top of the bowl (the steel form is upside down).

With luck, I’d get a textured array of “stumps” pointing up, somewhat reminiscent of the trees downed in eerily ordered arrays after the Mt. St. Helens eruption 20 years ago. (which is why I’m calling it “Stumpbowl”)

So, I cut a 15-inch round of 3mm clear, then–because it’d be hard to get a bowl to stand flat if there were little stumps all over the bottom–I put a circle of Pimento Red on the bottom, wide enough so it would show a bit of red border when the bowl was upright.

stumpbowlrodslumpsThen I drew some schwoops with a Sharpie, laid out a simple design, and started whacking glass rods. I whacked and whacked and whacked–how in the world do Mel Munsen and Giles Bettison chop glass cane ALL THE TIME when I’m about to die of carpal tunnel syndrome from doing one lousy bowl?–and ran out of glass rods before I was even a quarter finished.

Headed down to Bullseye looking for more (which is how I discovered I had freaky streaky striker rods–it’s only made once a year, apparently, and I lucked into a bunch of leftovers). The nice folks in the Resource Center dove into the basement or someplace and came up with their few remaining rods, and I supplemented them with another 30 or so in “standard” creme colors.

Back home, chop, whack, chop–my hands are getting really, really tired–and today (three days later) the layout’s done. I left some open spaces for contrasting texture, and those are filled in with mounds of medium Carnelian frit, which should strike to a nice burnt orange. The clear rod segments you see outlining the sections are actually orangy-red striker to pull together the center with the Pimento Red chunks in the layout. Couldn’t find a transparent Pimento Red–most of the transparent reds are too blue–so this is as close as I could get.

stumpbowldoneOne other thing: Light Peach Cream continues to be my absolute favorite “white,” and the rod form reinforces that. I work on a light table, and there’s enough translucency in LPC that the rods literally glow. It’s really a beautiful, beautiful color. When I get this stump thing down I’d like to do a piece entirely in this color. In fact, I’m thinking that LPC maybe a good way to work through my color thing with pate de verre.

Above is the blank, just out of the kiln and ready for its first slumping (it’ll take two slumpings to make it as steep-sided as I’d like). It’s backlit on my worktable so you can better see how the colors have changed in firing.

It was a fun exercise, nice change of direction.Getting the schedules right was the real challenge. The flat base encountering a tack-fused rod, sitting at right angles, would mean that both pieces would be contracting and trying to pull away from each other during cooling, setting up a LOT of stress potential.

I wasn’t sure that this design was even possible, so I took extra care with the schedule, annealing as slowly as if this were a 4-inch casting. I chose to slump OVER a metal form to get a fazzoletto (handkerchief) shape, which meant I was balancing the relatively stable center area (since it was all flat glass) on the mold but letting most of the blank hang out in space in the hot kiln, the annealing needed to be jo-block perfect to avoid thermal shock or annealing cracks.

My layup, therefore, was as conservative as I could get it; I surrounded the metal mold (my Kitchen Aid mixing bowl, which is a marvelous upside-down tulip shape) with upright firebrick, knowing they’d insulate the area between mold and brick, slowing down the heat. The circular blank just barely rested on the edges; as it slumped down, the glass would come off the brick and fall slowly.

I added fiber paper to the top of the mold, where the glass rested, to keep it from overheating. I considered baffling the heat coming from the top elements with a fiber paper tent, but in the end settled for an extremely slow upramp at relatively low temperatures. Then I let it sit there to process for some time.

This is what happened in the end. I don’t particularly care for the vessel–I think it looks like a wacked-out hooked rug from the 60s–but I got the tack-fuse right and the bowl has minimal stress in the polariscope. So it CAN be done…


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