Casting into the doldrums
February 21, 2008 by cynthia
Stuck in Castuary again, anticipating what’s coming out of the kiln after a looooooooooooong firing. Drat. I need stronger nerves.
I think what appeals the most to me about glass casting is getting away from thinking of glass as a shapeable 2D object…and the fact that every casting is, ultimately, an engineering puzzle.
- How do I build a model that takes advantage of glass’ physical properties (transparency, translucency, surface variability, etc.) without being caught by its limitations…and still tell the story I’m after?
- What method should I use to create a mother mold or resin model for archival purposes (i.e., in case I screw up and need to rebuild something)?
- How do I construct an investment that takes advantage of gravity to help the glass flow into the right places, without trapping air, wax, clay or whatever else I don’t want?
- How thick should I make the walls so that they hold the glass securely without overinsulating or causing hot and cold spots?
- Which investment(s) should I use?
- What schedule will get the glass juicy enough to flow smoothly into all those tiny details without boiling? Am I taking a fragile investment up too fast? Am I staying in the danger zones too long?
- Most of all, how do I develop enough patience to get through another Castuary?
Sorting out casting puzzles takes patience, knowledge, testing, a lot of help from my friends, and time.
I doubt that I’ll ever restrict myself to just casting, however much I love sculpting. In my world, it’s a tortoise-and-hare problem: I love what I sculpt to the point that I call it “heartwork.” But a colleague once said my motto should be “I want it NOW and I want it delivered!” and she was pretty close to the truth. The hare in my brain goes nuts with all this slow and patient problem-solving unless I let it out to play every once in awhile.
That’s probably why I do a lot of tack-fuses (and rarely work with plain old flat fuse-and-slump anymore), and probably also why I’ve got maybe four sculptures going at any one time and it takes so daggone long to finish one.
I keep thinking I should shortcut the whole process and simply send my models to somebody else to cast, like metal sculptors do with foundries. Somehow, though, that seems like cheating.
So…feeling a bit low this morning, I headed down to the studio and took inventory of what I’ve done in the last six weeks or so.
- HostaBowl has made great strides. The figures need a final casting, the wax model of the “bowl” is complete, I need to take a final mothermold for archival purposes just in case…and then it’s a matter of investing and filling the mold and getting it into the kiln for a loooooong, slow firing.
- Shout (ShoutingMan and his brother, on their mounts) is in the kiln and the proximate cause of my Castuary doldrums.
- Sunflower (the third in the Emergents tryptich) is nestled side-by-side with both Shout components in the kiln and not helping the doldrums at all. A peek into the kiln with a flashlight during ramp-up showed what looked like hairline cracks in one corner, which makes me VERY nervous. Maybe it was just a trick of the light… sigh
- Started a new series of keystone projects around BE rods. Nothing fancy, some interesting problems to work out (did you know that rods can vary in dimension by nearly 2mm?), but the first two out of the kiln in this series definitely meet the coolth test.
- Progressed with WeedsBasket and the whole stringer/support structure experiments. Made a huge boat of stringer and integral support frame. It was kinda ugly, so I think this technique works best with simple, uncontrived shapes.
- Wax components are about 7/8 cast to start on the paisley bowl, a combo casting-and-tackfuse that tests how to “weld” cast components together without distorting them. This one oughta be fun but it’s low on the priority list.
- Completed some very preliminary tests of methods to achieve smooth and transparent gradient fills in casting. Not particularly happy with this one, but tremendous food for thought.
- Ideas and preliminary sketches are complete for another Emergent, this one kinda based on a moebius basket, a caterpillar, and a ship’s bow that should be interesting. Ditto for HostaGoblet, although I still have to figure out how to either cast it in sections or graft another 3 inches onto the top of my kiln.
That’s not bad for someone with a more-than-fulltime dayjob. OK, I feel better.
I’m having the same problem with my glass. I spend almost two weeks working on a casting before I throw it into the kiln. The last run of the kiln lasted about ten days. I was so anxious to see the finished project that I started to break away the plaster silica mold while the glass was still warm! Clink! A crack where the glass was exposed to air. I need to learn to be more patient, especially after waiting a month for a piece to be ‘finished.’ I use bullseye casting glass with stringer inclusions. Do you know of a way to fix cracked glass? Hextal maybe?
Austin
Austin, I’ve learned the only thing you can do is walk away. Just walk away. No, walk away! That kiln is D-E-A-D dead until the little readout has said “OFF” for at least a couple of hours. I stay out of the kilnroom except for temperature monitoring, and once it hits the downcycle I pretty much stay away. Only way I can keep myself from peeking.
If you can separate the pieces, Hxtal might be a good choice to glue it back together, or if the crack is exposed to the surface you can use an old lapidary trick and let a thin, slow-setting glue like Hxtal seep into the crack and fill it. Since it dries pretty close to optically clear it can sometimes make the crack vanish.
Other option, though, is to reinvest the cracked piece–assuming you otherwise like it–and refire. Just make sure you get it really, really clean before you invest, and alter your schedule to account for a solid (and probably thermal-stressed) piece of glass.