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Opening The Kiln


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#1 ayjay

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Posted 01 October 2013 - 05:38 AM

I'd guess we are all somewhat impatient when it comes to opening up a kiln after firing, since my first few home firings I've managed to contain myself until the temperature drops to 100°C and then it's on with the gloves   ^_^   -(I usually crack the lid open a little at about 200°C to help speed things up a bit).

 

I've been thinking though, I use some of my  wares in a domestic oven, they are quite likely to be removed from the oven when it's over 200°C.

 

Is this any different to removing from a kiln at that temperature?

 

Is it just the first time after firing that it needs to cool down slowly to room temperature, or what?



#2 bciskepottery

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Posted 01 October 2013 - 06:08 AM

A ware removed from the oven, full of hot (and presumably tasty) food, will cool more slowly because of the heat mass of the contents than an empty ware removed from a kiln.  So, yes, there is a difference.  I'd recommend patience for removing from the kiln. 



#3 PSC

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Posted 01 October 2013 - 06:31 AM

I have a rule, if i can't touch the ware with a bare hand and lift it out of the kiln then it stays in the kiln. As a kid i also was perfectly fine waiting til daylight to get up and open my presents the santa brought me. ;)

#4 clay lover

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Posted 01 October 2013 - 07:19 AM

Glove is the clue, if you need them, it's too soon. Wait until you have the experience of listening to a full load sit and ping as the pieces contract quickly. That will cure you.
BTDT!

#5 oldlady

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Posted 01 October 2013 - 07:58 AM

the other problem is removal of shelves if it is a top loader.  reaching in to pick up a hot shelf is not a good thing to do.  wait.


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#6 ayjay

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Posted 01 October 2013 - 10:33 AM

A ware removed from the oven, full of hot (and presumably tasty) food, will cool more slowly because of the heat mass of the contents than an empty ware removed from a kiln.  So, yes, there is a difference.  I'd recommend patience for removing from the kiln. 

Is it really that simple though? You might take a casserole from the oven and almost immediately empty it onto several plates, surely that's very little difference?

 

I have a rule, if i can't touch the ware with a bare hand and lift it out of the kiln then it stays in the kiln. As a kid i also was perfectly fine waiting til daylight to get up and open my presents the santa brought me. ;)

You're just no fun at all!   I bet you never trim without a chuck either. ;)

 

Glove is the clue, if you need them, it's too soon. Wait until you have the experience of listening to a full load sit and ping as the pieces contract quickly. That will cure you.
BTDT!

Spoilsport! That's what gloves are for. ;)

 

I cracked the lid open a half inch @ 200°C  and did then wait until it was down to 80°C  - there's no pinging - making a cup of coffee is hotter than that -  the controller is still telling me it's HOT @ 55°C I can pick  up @ 55 with my bare hands.

 

The shelves are not too much of a problem, there's enough room for my pinkies down the sides, even with gloves.

 

Please insert whichever smilie conveys my sense of fun and my desire to not have caused any offence.



#7 TJR

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Posted 01 October 2013 - 01:07 PM

I have a rule, if i can't touch the ware with a bare hand and lift it out of the kiln then it stays in the kiln. As a kid i also was perfectly fine waiting til daylight to get up and open my presents the santa brought me. ;)

My mother was a nurse. She always worked Christmas day as she got double time pay. We were allowed to open one gift and one gift only,on Christmas morning. I chose the biggest box under the tree,thinking that it was an electric train set. Wrong. YOU try playing with a pair of suit pants all day until your mom comes home.

Just sayin'

TJR.



#8 Mart

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Posted 01 October 2013 - 01:16 PM

If we get busy, I have to crack the lid at 200 C or so and then a bit more at 150-120C or our 24 h cycle will go out of whack.

#9 neilestrick

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Posted 01 October 2013 - 01:24 PM

If God didn't want us to unload hot pots, he wouldn't have invented gloves. I open the lid at 300F (148C) and let it cool from there if I have time, but often just unload with gloves if I don't. I work with porcelain, and nothing cracks.


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#10 bciskepottery

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Posted 01 October 2013 - 01:52 PM

"I cracked the lid open a half inch @ 200°C and did then wait until it was down to 80°C - there's no pinging - making a cup of coffee is hotter than that - the controller is still telling me it's HOT @ 55°C I can pick up @ 55 with my bare hands."

 

Your controller measures ambient heat/temperature in the kiln . . . kiln shelves and wares sitting on them can be hotter than what the temperature reads because they are more dense, hold more heat, and take longer to cool than the ambient air inside the kiln.  And, if you use a temperature offset for thermocouple covers, keep that in consideration. 

 

And, I have burnt my hands more often from spilled coffee/tea than I have from removing pottery and shelves from my kiln. 



#11 Mark C.

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Posted 01 October 2013 - 02:15 PM

If you are making a living from this or in a time cruch with students and classes-I see the rush -if not why hurry.

Yes I have kevlar gloves but if I do not have to have the load I never hurry the cool down-I used to but matured over time.

Whats the rush if it does not matter when. 

This said I hade to unload my 35 cubic car kiln the day after firing and cracked it at 5oo about 1/2 inch-then let it cool down-never having to use gloves-Leaving for a show soon and needed to pack it up.

I have done the gloves with a electric bisque but the ware is less problematic in bisques.

No hurry -no worry

When you dunt some wares then you will know the limits until then its ok.

Mark


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#12 Kohaku

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Posted 01 October 2013 - 03:24 PM

If God didn't want us to unload hot pots, he wouldn't have invented gloves. I open the lid at 300F (148C) and let it cool from there if I have time, but often just unload with gloves if I don't. I work with porcelain, and nothing cracks.

 

When I first started firing in my own kiln, I was desperately, hopelessly impatient. I once opened and unloaded a kiln at 600F. Insane, stupid, etc. etc. My leather gloves were literally smoking when I put some of the wares down on the ground.

 

Nothing ever broke or dunted... not one single thing.

 

I was lucky not to severely burn myself, though. I chalk it up to my immaturity and hastiness as a 40-year old. Now that I'm a mature 43, I have a firm rule to avoid the studio when the kiln is cooling, and give things a full day past the end of the cycle before I walk in.

 

Treebeard would be proud.


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#13 ayjay

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Posted 01 October 2013 - 04:11 PM

Well at least I'm not alone in this, (never thought I would be), I expect I'll carry on doing it my way, it's been OK so far if I don't push it too far.

 

I'm yet to be convinced that taking something from a domestic oven at over 200°C is any different to taking it from a kiln @200 - but I'd soon run out of places to put so many hot pots anway so I won't be doing that. ^_^

 

 

Your controller measures ambient heat/temperature in the kiln . . . kiln shelves and wares sitting on them can be hotter than what the temperature reads because they are more dense, hold more heat, and take longer to cool than the ambient air inside the kiln.  And, if you use a temperature offset for thermocouple covers, keep that in consideration.

I'm sure your right about the science but I do know that the temperature display on my controller is very sensitive;  with the controller turned on but the kiln turned off, a few seconds with a hairdryer blowing through a bung hole will show a rise in the temperature, it also takes a long time after a firing for the controller display to match the ambient temperature outdoors (kiln is in an unheated garage),  the kiln bricks are still retaining heat and the contoller is showing me exactly that.

 

Many thanks for all your input.






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