Skutt pulls the thorn (kiln update)

>, pate de verre, studio practice>Skutt pulls the thorn (kiln update)

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?”

Yeah….

“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.

2014-09-08T21:09:54+00:00

6 Comments

  1. cynthia August 26, 2009 at 2:22 pm - Reply

    Oh well, my two obsessions in life appear to be working in glass and fighting with computers. I learned long ago that the best way to enjoy either was to learn to enjoy being embarrassed on a regular basis.

    And I still may opt for the controller–there are some powersaving features that are really attractive. I just prefer not HAVING to buy it until I’m ready, so this is nice.

  2. jenn houser August 26, 2009 at 1:13 pm - Reply

    I think a tiny touch of embarrassment is worth the price of not having to purchase a new controller. I wouldn’t have come up with that solution either.

    Glad it wasn’t worse.

  3. cynthia August 25, 2009 at 9:17 am - Reply

    Casting’s a bit different because you have to dry the molds first and get the moisture/burnout/etc. out of the kiln before it can settle on the elements or the glass and mess things up. In my case, I’ve usually got somewhere between 8 and 16 hours in my first segment drying cycle. Most of my stuff is pate de verre, where you not only have water in the mold from just mixing the plaster, you usually ADD water to ensure that the glass powder sticks properly–so these tend to be very wet molds.

    Perry and I discussed several possible solutions, i.e., installing a venting system in the kiln so I don’t have to crack the lid during the dryout segment, replacing the elements, jiggering the schedule a bit or running two separate schedules, providing a windbreak in front of the kiln, etc… I’m going to run some tests on just how wide the lid really needs to be open to vent properly–I may be able to get away with less.

    For now, the best idea seems to be simply keeping the garage door closed whenever I’m venting the kiln on a drying cycle. Open the lid, close the door. Close the lid, open the door. Doesn’t do much for my clever venting solution, i.e., vent to the open air so I don’t have to breathe whatever’s burning out of the kiln. There may be an exhaust fan in my future…

  4. Ed LaPlante August 25, 2009 at 8:05 am - Reply

    I know of fusers who have their kilns on back patios in cold climates???

    We have two Evenheats right at the front of our studio and run them to 900 with the shop doors open and the lids propped all of the time in lots of different weather.

    It might be the location of our kilns vs doors or the location of the thermocouple, who knows. If I had this problem I would have to try shielding part of the opening closest to the outdoors. We use our studio for multiple functions including my sign shop. I could not imagine firing with out the front and back doors open and fans going. It is way too hot as it is.

    Ed

  5. gary August 25, 2009 at 7:39 am - Reply

    Just like bug-fixing on a computer, ain’t it? “No… I’ve not changed ANYTHING to make the program crap out.” “Nothing?” “No, just had 15 other programs running this time, but that shouldn’t matter….”

    Let’s see, what is it I’m thinking of…. yeh… “Look for the simple solution. It’s usually the correct one.”

  6. Kat August 25, 2009 at 7:32 am - Reply

    Glad it was easy. Too bad you didn’t know that on Saturday.

Comments welcome! (thanks)

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