Saturday, January 10, 2015
failure rates and learning curves
To answer Ms Moon's question, what do I do with the ones that don't pass muster?
Well, I don't finish them for one thing. They usually go on a shelf somewhere until they get put in a box and eventually thrown away. This one will go next to another oleander failure, one that was over-fired. The last time we did one of these we had to do it twice.
This is how the turquoise bowl was supposed to turn out.
If it's a casting defect and I think I can salvage it with a little creative cold work, I'll make the effort but mostly a bad cast can't be remedied. This piece cast well but the colors didn't work out. That in itself, while disappointing, is not an immediate reason for rejection. I've sold many a small bowl whose colors didn't come out the way I envisioned. But on this one, the colors were just too extreme on the one hand, the blue, and the white did not show up adequately and was pixelated to boot and when illuminated from above nearly disappears altogether.
Failure is always a possibility with this technique and now that we are only doing one of a kind pieces, that danger is a little more present. When we were doing the small bowls, a form we had done over and over, a couple hundred times, we got so good at them that our failure rate was almost non-existent. But when we switched to a taller form, I stopped trying the 6" tall vase because after the first two that came out perfect, we couldn't seem to get one that didn't need extensive cold work. The last one we made was so perfectly cast except for the top inch and a half which was a total ruin that it made me cry.
And while most of the failures come from bad casts...over-fired and full of pits, under-fired and granular, mold cracking during firing, not holding at the casting temperature long enough...other failures come from how the mold was filled...too much glass overall, not enough glass, not enough of a color or too much of a color, mixing colors together that react badly with each other, putting a dark color behind a light color. And then there is always the mold itself which can be weak and full of bubbles if not made properly.
I know that every time I try a new form, like the boxes, I'll have a few failures so I try to ease into it. I'm trying to do things that are simpler in some ways...no more two and three part molds. Well, two part molds but easier two part molds. These days I'm doing work that can be cast in open face molds, the easiest of all.
This technique is the most difficult, time consuming, detail oriented, and sometimes frustrating thing I have ever done, and infinitely rewarding when it all works out right. It's a good thing there were two of us while we were working on our learning curve because there were many times when one of us was ready to give up. Fortunately, neither of us were ever ready to give up at the same time.