Convergent Series

learning, using & teaching metal clay, and other aspects of life

Update on the Lifespan of a No-Flake Foil Firing Box

Posted by C Scheftic on 2014/02/10

A few days ago, I was talking with another metal clay artist about how I fire bronze, copper,and steel in vessels I “fold” myself from sheets of steel “no-flake” foil, when I realized it had been two years since the last time I’d mentioned them here.

Which I find interesting: in three years, I’ve used three boxes! Counting them up, I figure I put a box through a firing somewhere between 1 and 2 times a week, on average. But few things in my life are average…! No, really, it’s more like 6 or 7 times a month, but even that tends to happen in maybe two “bursts” of several firings in quick succession, then it’s several weeks before I do that again.

Something I learned from my first no-flake foil box, plus discussions with others after I wrote about that, is that the foil tends to crack open along the top edge of however much carbon is typically used. So, with my second box, I started out by piling the carbon a a little bit higher than I’d been doing. Then, when some cracking started to appear, I could just lower the level a bit, and get a number of additional uses out of it (because the holes–eventually stretching into a longer tear–were then above carbon, it didn’t leak out)! With the extra firings, it also began to crack along the top-most folds: what that meant is that I tried to be a bit more careful as I handled it, especially when moving it in and out of the kiln. Eventually, though, I decided I was carrying conservation perhaps a bit too far: after at least 75 firings over the course of a year, I took its picture and retired it!

Box #3 has lasted even longer! It has handled 80-some firings over almost 14 months. I did not keep fully-detailed records but, between the notes I do have and my general memory of the past year, I’d say that for its first year, I did a higher proportion of firings in the mid-fire range, and a smaller share in the high-fire range, than I had done with the first two boxes. That seems to have reduced the number of little holes it developed, so there were fewer to spread into wide-open cracks.

That is, until the start of this calendar year. That’s when I started playing with Hadar’s One-Fire High-Fire Trio. The single firing needed to both de-binder the clay and sinter the metals is a real treat, but when I started firing batch after batch in the high range, I noticed that the sides started warping out. So, even though Box #3 does not have any big holes, it is now being retired because I can barely fit it in he kiln any more: it is in danger of hitting the kiln’s thermocouple!

But. I still think that these boxes are well-worth their cost! Do you?

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