It makes sense, but I’m having trouble believing it: My kiln failed because I left the garage door open.
Skooby-the-Skutt bathtub kiln died right at the start of an important pate de verre firing last Saturday. Since I’d bought him a brand new controller not four months ago, I was pretty unhappy about it, and left a flurry of HELP messages with Skutt.
“Hmmmm,” said Perry-the-kilngod when he called first thing Monday morning, “I read your message(s) and I’ve been thinking about what might have gone wrong. Do you have a voltmeter?”
Of course I do. I’m a geek.
“Good. Start up the kiln and let’s check the voltage…” which was fine. Nothing was loose, elements weren’t too frantically resisting the current… “which tells me there’s not much wrong with the controller OR the elements. So…tell me about HOW you fire.”
I went through the entire pate de verre firing process in detail (adding that the last 12 firings went perfectly with just that process).
“Hmmm. Do you always have the kiln lid propped up so far for the first segment?”
Yeah. My molds are packed wet, and if I dry them too much outside the kiln, moving the mold can jostle the powder-coated frit and cause it to fall to the bottom of the mold.
So I put the very wet molds in the kiln and dry them in place, propping the kiln lid up about 3-4 inches. This lets all that water vapor burn off without jostling the frit pack. I usually close the kiln somewhere between 600 and 1000F.
“And that’s never given you a problem before?” Nope. “So has anything changed since your last perfect firing?”
“Not a thing,” I insisted, “Well, I did remodel the garage and put most of my casting processes out there with the kiln, but that wouldn’t affect the controller, right?”
“Wait…you’re now working in the same room while the kiln is firing, with the lid up? In the summer? Doesn’t it get pretty hot?”
“Naaaah–I just open the garage doors to let the heat out. It’s actually quite comfortable.”
“AHA!” says Perry, with a chuckle. “It was cool and breezy this weekend, wasn’t it? Is the kiln controller right by the garage door?”
“So the wind is blowing air into the kiln, right over the controller, and that’s where we put the thermocouple. This is a longshot,” Perry mused, “but I think you’ve got cold air flowing into the kiln and altering the temperature readings at the thermocouple.”
“The breeze wouldn’t bother the controller if the lid were closed, but if the kiln were open the controller might get confused and think the elements weren’t firing. That would cause an error message and shutdown. Why don’t you try the same schedule with the lid completely closed, right now? Let’s see what happens.”
Closed the lid and started her up. Worked like a charm.
“Oh, yeah!” says Perry, kinda smugly (I don’t blame him), “That’s the problem, alright. When you’re venting the kiln, close the garage doors. Problem solved.”
And here all these years I’ve been saying it doesn’t matter if you fire your kiln in Alaska or Tahiti because either way, the environment inside the kiln is a helluva lot hotter…
…unless of course the lid is open.
Sigh. Do I feel dumb?
I’m not going to answer that.