Raku Pottery Question. Is it okay to stop the kiln and remove pieces that are done, and then restart the kiln to finish the other pieces?
April 30, 2010 6:37 AM   Subscribe

Raku Pottery Question. Is it okay to stop the kiln and remove pieces that are done, and then restart the kiln to finish the other pieces?

I'm an amateur potter, self-taught, and have been experimenting with Raku for a couple years now.

I recently purchased a different brand of glaze, and during the firing I noticed that the new glaze seemed to 'liquefy' much sooner than the glaze I had been using. The pieces with the new glaze were bubbling (ferociously), while the other pieces were still getting smoothed out.

Since the other pieces I was firing weren't done yet, I left the whole lot in there until all the pieces were sufficiently.

And, of course, the pieces with the new glaze totally ran and didn't turn out as nice as I think they would have had I removed them earlier in the firing.

Do you think it will it ruin the pieces whose glaze isn't 100% done to shut the kiln down, remove the done pieces, and restart the kiln?

If you found yourself reading this far and were still wondering how Raku works, this link will give you a pretty good idea of the process, the equipment, and the things I make. I made this website to present the Raku process to a class of 6th graders. It shows the kiln and has a couple short videos on the process.
posted by bricksNmortar to Sports, Hobbies, & Recreation (9 answers total) 1 user marked this as a favorite
Every raku firing I've seen has involved opening the kiln, grabbing pieces that need to come out sooner, and closing it back up and continuing. Sometimes the remaining pieces are rearranged. No need to shut it down. Knowing where the hotter/cooler spots are in your setup helps.
posted by wens at 6:46 AM on April 30, 2010

Why turn the kiln off? Just remove (carefully) the finished pieces and let the others continue on. This is how I've always done it, and while I suppose it's a bit wasteful of gas, I've never had a problem with the kiln or the pieces.

I suppose you could turn the kiln off, but some glazes get crawly when they are cooled and then restarted. So I like for them to at least have some heat on them, while I'm pulling out the finished work.

As to your (unstated) glaze question: glazes will tend to melt at different times (even for the same rated cone) depending on the ratios and ingredients. If you've got a local glaze calculations freak, you could ask them to help you tweak the molecular ratio of the glazes so they melt at the same time.
posted by 1f2frfbf at 6:50 AM on April 30, 2010

It is a good idea to turn the kiln off while you use the tongs because the elements are bare 220 volt wires.
posted by weapons-grade pandemonium at 7:20 AM on April 30, 2010

Oh, I see you have a gas kiln.
posted by weapons-grade pandemonium at 7:21 AM on April 30, 2010

I would be very wary of sticking tongs into a lit gas kiln. That's just asking for an accident. But if you turned it off, pulled the lower-temp work, and then quick got the kiln going again, I think you'd be fine. Ideally, you would simply do two separate firings. . .

Are you buying commercial glaze? That would make it hard to recalculate (if not impossible). But any supplier worth their salt can make sure you've got glazes that are all in the same range.

Good luck!
posted by dirtmonster at 10:06 AM on April 30, 2010

Thanks for all the encouragement. I kind of felt that it would be okay, but it never hurts to see if someone else has tried it.

I do use commercial glazes. Recalculating is not in my pottery vernacular yet. I've never had this problem before, it was just until recently when I bought some glaze from a different manufacturer than I had been using.

posted by bricksNmortar at 10:32 AM on April 30, 2010

I always left the kiln on. Obviously you need to be freaking careful.
posted by Nothing at 1:42 PM on April 30, 2010

I am a (sadly former) potter, but I always did high temp firing and never raku (although my grandmother does raku, but I cant ask her right now).

That being said, can't you just put the pots with a lower temperature glaze in a different cooler section of the kiln, or do a firing based solely on pieces with similar cone ratings (do they use cones in raku?)? Two thing we do in high temperature firings (around 2300) were 1.) make sure that all of the clay and glaze were appropriate for that temperature and atmosphere 2.) for runnier glazes (such as ash based ones) you put them on pieces in a manner that accounts for the fact that they will run all over the place, so you might build some "gutters" into the work so that they run in a way you can account for.

Also remember that you can pass of mistakes as "wabi sabi" which is roughly translated as "beauty of the irregular" and is a revered artistic aesthetic in Japan.
posted by BobbyDigital at 2:20 PM on April 30, 2010

When I've done Raku firings in the past, we always took pieces out (and put them in) while the kiln was firing. If you're putting them in the kiln part way through the firing, make sure to warm them up (e.g. letting them sit on top of the kiln) first to keep them from cracking.
posted by JiBB at 2:46 PM on April 30, 2010

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