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Anders

Kiln Opening Temp

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Hey Ceramiacs

 

I've been reading about the topic on the net, and it seems that there are very different opinions on subject. 

I was wondering if someone had a more scientific approach to the matter. 

 

Some say that you should open at 130F, and I think that is a little strange because that means that if you make a cup,

 you have to mind the temperature of you coffee, and other hot things you may consume of you pottery.

 

If you open the kiln at 150f and hear crackling, isn't that a coincidence. I mean if the kiln are outside and it is freezing, I see how it might play a role.

But it just seem strange that ceramics that reach red hot temperatures are sensitive too degrees that low .

 

thanks,-] AC

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I think the care is taken for two things ... The pots and the kiln elements ... Neither like being shocked by colder air.

I have been taught it is usually considered safe to open a kiln once the temp drops below 200 F .... Bearing in mind the bottom might be hotter as it holds the heat. If your pots ping then... well they were going to ping later too.

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I have developed a method I like to use for opening a kiln to even temp.

 

I cut off my vent when kiln cuts off at cone 6. Let it cool naturally to 250. Once it reaches 250. I turn on my vent and remove the 2 peepholes. It cools the rest of the kiln pretty quickly and within an hour it is below 150 usually. I like this method because it is evenly cooling. There isn't a huge gust of air coming into the kiln from just yanking pots out.

 

It is also nice and easy to handle with some basic gloves. I used to open at 250, which is what most people do, but I found that the bottom of the kiln was still rather hot, so I developed this method of cooling. It works for me pretty well. Waiting on the kiln to cool below 250 naturally can take like a long time to hit 150s.

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For glaze loads, I like to wait until the kiln is around 100F.  The thermocouple readings are of the air temperature in the kiln; your wares and shelves are likely hotter than that reading.  My thermocouple have a protective sheath; so, they have an adjustment in the controller to compensate for that as they are not reading the actual inside temperature and the offset helps prevent over-firing.  And, for the most part, I'm over the "Christmas" rush of every kiln firing  -- mostly because my kiln is electric and I've settled on a smaller palette of glazes that are consistent in firing.  Letting the kiln cool a bit longer is no big deal. 

 

If you induce pinging by opening the kiln when it was too hot and allowing a rush of cold air . . . that does not mean the glaze would have pinged if it had been allowed to cool further before opening.  Some glazes will ping regardless.  Some pinging can be from operator error. 

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  And, for the most part, I'm over the "Christmas" rush of every kiln firing  -- mostly because my kiln is electric and I've settled on a smaller palette of glazes 

I've decided I'm a Christmas rush junkie.  I find something I like and works and then I'm on to the next experiment.

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We crack the lid on our kiln at 300F and 150F we open it up.

 

We will put gloves on and start pulling items out around that temp. 

 

We throw stoneware.   Our stoneware is micro/dishwasher safe and can be used in the oven.    if your items are designed to be used in the oven (bake ware)  then they should be able to be removed from the kiln at 300+.

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When thinking about oven ware, remember: a casserole removed from the oven at 325F and filled with mac 'n cheese (or your favorite dish) will cool much slower than an empty casserole removed from the kiln at the same/near temperature. What is most important is having a good clay body and glaze fit . . . where both expand/contract together with heating and cooling -- whether in the kiln or in the oven.

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If there's no rush to get the pots out just let the kiln cool naturally to room temp. What the point in spending all the time and energy creating/finishing/firing/etc, to rush a cooling only to damage wares/elements/furniture just to save a couple of hours.

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My kiln is in our garage. So it depends on the season. Right now, being so cold out, I wait til it gets down to 100* than open it and unload it. In the summer when it's really hot out there, I'll prop the lid and pull out the peepholes around 300*.

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for the bisque electric kilns we raise the lid about an inch when it reaches 200. after that, it gets unloaded when its cool enough to unload without gloves. for the gas highfire glaze kilns, they fire friday, unload monday morning so anyone who wants to be there can see the load as it comes out. . as a group studio we kind of have to have a schedule since there is work of many people in each load including kids stuff.  rakuku

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