Crash Cooling...Deliberately

[curt]

How fast is it possible to cool a kiln from stoneware temperatures?   Are there limitations as far as the kiln is concerned?  Maximum cooling speed?

Pretty sure this would be very hard on kiln bricks, shelves, props, etc., so let’s assume I am firing a FIBRE kiln with sacrificial kiln furniture (or none at all) and ware that is impervious to thermal stress.

What is to stop me firing to top temperatures and then shutting down and then, say, running the kiln vent full blast for several hours?

I have read industry does this kind of thing regularly, with incredibly fast “cool-to-cool” firing times.  And we know that raku firings are basically this.

Trying to see if it is possible to fire a kiln from 5pm start to midnight cone 10 then shut down cool it to be able to open and unload it by, say, 7am the next morning.  Dealing with kiln issues first, worry about what kind of ware later...

Thoughts?

[oldlady]

remembering all the ads on the back cover of ceramics monthly magazine, i recall Skutt kilns talking about a tile company that turned around new tiles in a day.   why not contact skutt?   or if your kiln is not home made, its manufacturer?

[JohnnyK]

There is nothing to stop you from doing anything, Curt...If it is a fibre kiln, I would guess that you are firing with gas. I would also guess that it is going to take less time to get it up to cone 10 than a kiln with bricks. It should also cool down faster than a brick kiln. So again guessing that the kiln is easy to open (like a Raku kiln), why not just open it to the atmosphere and ambient temp?

In ceramics you constantly hear the mantra "TEST, TEST, TEST"...Just try what you want and look at it as another test. You'll find out soon enough what works and what doesn't...

JohnnyK

[neilestrick]

It would all depend on what type of clay you're using, what forms you're firing, and how thick and evenly constructed they are. Lots of variables. Remember that raku firing uses very under-fired bodies, which handle thermal shock better than vitrified bodies.

I've got a little test kiln that I can get to cone 6 in 5-6 hours, and it can cool fast enough to unload 5-6 hours later. It's so small that there's not much mass to cool down, though. My big kiln takes more like 32 hours to cool because of how much work is in there. Cooling it by pulling air though is a tricky situation, because it won't cool evenly that way. You can crash cool down to red heat without much problem, but getting through quartz inversion in a rush is tricky.

If I remember correctly, tile companies that turn them around super fast are dry pressing the tiles under extreme pressure, which makes for a very stable form. Plus tiles have very low mass, and if they're doing non-vitrified wall tiles, they don't have to worry much about warpage.

[curt]

Don’t have a specific kiln in mind for this yet.  Just exploring what may be possible for the moment.  Also keen to think it through as much as possible before actually exposing any kiln to this kind of treatment! 

So far it seems straightforward. Kiln will cool as fast as you want.  Low thermal mass of fibre enables quick cooling, and presumably the kiln frame can take it.  Open the door, blast the kiln vent, use whatever method you want to cool it down fast.  I take your point about uneven cooling but the idea is that simple forms can accomodate differing temperatures....hopefully.

Neil is your test kiln brick lined, and if so have you noticed any degradation from fast cooling?  (In it, or any other kilns you have examined?)

So that brings us to the ware.  Tiles are what I am thinking of, and possibly kiln shelves - or pieces of kiln shelves cut up - that would hopefully take the thermal stress.  (or that you wouldn’t mind terribly losing if they cracked.)

would start with standard stoneware bodies and if they didn’t survive look at formulating hardier body recipes.  As you said Neil, raku bodies are different:  grog-ier and more open, and not intended to go to full vitrification.  If quartz inversion is the danger zone, then maybe look at low silica, high alumina body recipes to reduce this risk?

the dry pressed tiles are interesting, will investigate further, ie how much pressure to form, etc..  

 

 

 

[Mark C.]

I crash cooled a kiln in the very early 70s-cone 10 fire-the kiln was a catanary arch.After the cones fell I unbricked the door some. The kiln was cool in a few hours. All the pots came apart-the clay body could not take it. I did not kiln the kiln furniture but did shorten its life. Lesson was see where the limits are and now I know Not to do that again.

Your lesson will also tell you the limits for your clay body.-

My kiln then was hard brick and gas fired-The crash cooling is hard on everything

 

[Denice]

I have a tiny test kiln like Neils that has the thin brick walls and cools fast.   I bought the kiln in 1998 for testing glazes,  I soon realized that my glazes were different than the test samples.  At first I thought I had made a mistake in measuring  after double checking that and many other scenarios I determined it was the fast cool.   The kiln is so small it was difficult to down fire,   couldn't afford a new test kiln so I just started cooling the bigger kilns a little faster not a crash cooling.  I work with a clay that will take that kind of abuse.   The bricks in the big Skutt and test kilns are in good shape,  I did have to toss Paragon last year because the bricks were disintegrating.  The kiln was 45 years old so I don't know if cooling faster was a factor.      Denice

[Min]

There was an interesting article in Ceramics Industry from Larry Cam. His company fast fires from ambient to ambient temps in 3 hours or less, bisque, glaze and decal firings. He stresses how the LOI of both claybody and glazes are  important as are the schedules and heatsinks. He uses a deflocculated casting slip that is then press molded into plates etc. Full article here, including graph of firing / cooling schedule. I'm thinking that if you just want to crash cool and not fast fire the firing and cooling ramp could be useful. (There is a contact link to Larry Cam at the bottom.)

[liambesaw]

Dinnerware manufacturers that I've seen do the super short firing cycle also don't use a normal kiln, it's a conveyor system that pulls the items through a long kiln where different zones along the conveyor blast them with different heats.  So the kiln itself isn't crash cooling, the plates just move out of it to cool in a controlled manner. You can look on YouTube for examples, I've seen quite a few factory setups like that.  

[Mark C.]

2 hours ago, liambesaw said:

Dinnerware manufacturers that I've seen do the super short firing cycle also don't use a normal kiln, it's a conveyor system that pulls the items through a long kiln where different zones along the conveyor blast them with different heats.  So the kiln itself isn't crash cooling, the plates just move out of it to cool in a controlled manner. You can look on YouTube for examples, I've seen quite a few factory setups like that.  

Yes the car moves thru the tunnel kiln-many products are made that -kiln shelves included.

[liambesaw]

1 minute ago, Mark C. said:

Yes the car moves thru the tunnel kiln-many products are made that -kiln shelves included.

Yeah. I don't know if we can exert that level of control over the firing and cooling process at home in our gas and electric kilns, it's apples and oranges from what I can tell.  

Their clay bodies are designed by scientists to fire exact in their system, I'm guessing without free silica in the end product in order to minimize the chances of quartz and cristabolite inversion issues, etc.  I'd love a chance to tour a facility like that, I might try to arrange that on my next trip to Japan.

[neilestrick]

6 hours ago, Denice said:

I have a tiny test kiln like Neils that has the thin brick walls and cools fast.   I bought the kiln in 1998 for testing glazes,  I soon realized that my glazes were different than the test samples.  At first I thought I had made a mistake in measuring  after double checking that and many other scenarios I determined it was the fast cool.   The kiln is so small it was difficult to down fire,   couldn't afford a new test kiln so I just started cooling the bigger kilns a little faster not a crash cooling.  I work with a clay that will take that kind of abuse.   The bricks in the big Skutt and test kilns are in good shape,  I did have to toss Paragon last year because the bricks were disintegrating.  The kiln was 45 years old so I don't know if cooling faster was a factor.      Denice

This is an excellent point. I fire down in my baby kiln, to match the slower cooling rates of my bigger kilns. My glazes look terrible when cooled fast. Just awful.

[Stephen]

On 10/11/2019 at 9:48 AM, curt said:

Don’t have a specific kiln in mind for this yet.  Just exploring what may be possible for the moment.  Also keen to think it through as much as possible before actually exposing any kiln to this kind of treatment! 

 

aah, like Johnny I thought you were wanting to do this with a current load. Another option is to have more than one kiln. It works well using a couple of kilns in tandem and no surprises from rushing things. One thing that I always worry about is unseen issues that my customers may find later.