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EKasse

Is my kiln cooling too quickly?

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Hello  - hope someone can help my query.  I have a feeling my kiln is cooling way to quickly.  I have a very basic kiln controller for my electric top loading kiln (potterycrafts).  This does not allow me to control the rate of cooling at all and I've noticed that my kiln cools quickly (from  1220c to 130c) in about 10 hours.  Is that very quick?  Once it reaches around the 200c mark it can then take all day to completely finish cooling.  Just FYI, i do soak the kiln  for about 30 mins once it hits the top temperature..

I think this affecting my glazes - I've noticed way more than usual pinholing and cratering in my cone 6 glazes (never had much of a problem with this before).  Plus I'm finding it almost impossible to find a satin matt glaze at Cone 6 to work - everything is way to glossy for my liking.   

Would investing in a better kiln controller that will allow for controlled cooling help me with these issues?  

Any advice would be warmly welcomed - but please go easy as i'm no expert on kilns -  Thank you!

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Your kiln cools the speed it does  because of its thermal properties. Unless you acquired some holes, it likely has cooled this speed all along. Thermal mass also affects its rate so bigger kilns can cool slower due to more stored heat. True matte glazes are always matte, even over fired they are runny mattes. Getting a matte look by slow cool usually requires firing down and generally affects crystal growth in some, not all glazes. Many people enjoy tuning the look of their glazes this way so it often requires  a controller that can fire down or a bit of hand firing work in the case of a manual kiln.

there are many matte recipes on Glazy, if true matte they will be matte regardless of cool down.

I have attached two true matte recipes below. I know they are matte because they were built with less than 5:1 silica to alumina ratio and we have used them in our test kiln which cools super fast for over a year now. The second recipe is a slight modification of the first (more boron)  to make it work better over heavy underglazes and a slightly more satin look.

finally holding at the top of your firing even though intuitive often does not cure pinholes and can lead to over firing. Assuming you use cones, what are you firing to?

I left out one answer, our little test kiln will go to cone 6 in five hours and cool to room temperature for a total of twenty hours. 

816B7937-B0C5-4FB1-99DB-A64FC4FF5D3D.jpeg.b93047dfd4c6ea728cfa22b672a5d8c8.jpeg223B27DF-593B-44BF-9360-9C39A73B12AF.jpeg.bf35fa3d4c80c5920d67415cefca0362.jpeg

Edited by Bill Kielb

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Thank you Bill

1 hour ago, Bill Kielb said:

Your kiln cools the speed it does  because of its thermal properties. Unless you acquired some holes, it likely has cooled this speed all along. Thermal mass also affects its rate so bigger kilns can cool slower due to more stored heat. True matte glazes are always matte, even over fired they are runny mattes. Getting a matte look by slow cool usually requires firing down and generally affects crystal growth in some, not all glazes. Many people enjoy tuning the look of their glazes this way so it often requires  a controller that can fire down or a bit of hand firing work in the case of a manual kiln.

there are many matte recipes on Glazy, if true matte they will be matte regardless of cool down.

I have attached two true matte recipes below. I know they are matte because they were built with less than 5:1 silica to alumina ratio and we have used them in our test kiln which cools super fast for over a year now. The second recipe is a slight modification of the first (more boron)  to make it work better over heavy underglazes and a slightly more satin look.

finally holding at the top of your firing even though intuitive often does not cure pinholes and can lead to over firing. Assuming you use cones, what are you firing to?

I left out one answer, our little test kiln will go to cone 6 in five hours and cool to room temperature for a total of twenty hours. 

816B7937-B0C5-4FB1-99DB-A64FC4FF5D3D.jpeg.b93047dfd4c6ea728cfa22b672a5d8c8.jpeg223B27DF-593B-44BF-9360-9C39A73B12AF.jpeg.bf35fa3d4c80c5920d67415cefca0362.jpeg

Thank you Bill for this reply and for the glaze recipe suggestion - looks exactly what i'm after.  I'm experimenting with Cone 6 glazes at the moment.  Can i ask - Marcia's Matte - i cant find this on Glazy - do you have the link please?

As for the pinholing/cratering - so you don't think it's got anything to do with the speed at which the glaze cools?

thank you :-)

 

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2 hours ago, EKasse said:

Hello  - hope someone can help my query.  I have a feeling my kiln is cooling way to quickly.  I have a very basic kiln controller for my electric top loading kiln (potterycrafts).  help me with these issues?  

What kind of controller do you have?  Even the most basic should allow you to do a slow cool, but it might be time-consuming, fiddly, frustrating, or all three.  I had a simple three position rotary switch and temp dial, but managed.  It's undoubtedly easier with a10 programm 9 ramp digital controller but more costly.

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Since your kiln has been cooling this way for some time and I assume you have not had pin hole issues I would say likely no. How long have you been holding at the top temp for thirty minutes ( often exasperates pin hole problems),  do you use cones and if yes what final cone do you fire to?

better yet, what has changed in your firing, glazes, claybody, bisque schedule since the pin holes?

glazy link below, but use the spreadsheet recipe if going over heavy underglaze.

https://glazy.org/recipes/19734

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3 minutes ago, Chilly said:

What kind of controller do you have?  Even the most basic should allow you to do a slow cool, but it might be time-consuming, fiddly, frustrating, or all three.  I had a simple three position rotary switch and temp dial, but managed.  It's undoubtedly easier with a10 programm 9 ramp digital controller but more costly.

It's the TC1800 - http://www.rlkilnservices.co.uk/controller_manuals/Studio 1800 Manual.pdf - i've just had another read through the manual and can't work out if i can slow the cooling with this controller.  i'm pretty sure i can't.  i would be delighted if i could be told otherwise!

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6 minutes ago, Bill Kielb said:

Since your kiln has been cooling this way for some time and I assume you have not had pin hole issues I would say likely no. How long have you been holding at the top temp for thirty minutes ( often exasperates pin hole problems),  do you use cones and if yes what final cone do you fire to?

better yet, what has changed in your firing, glazes, claybody, bisque schedule since the pin holes?

glazy link below, but use the spreadsheet recipe if going over heavy underglaze.

https://glazy.org/recipes/19734

Bill - sadly that link doesn't work - but thanks for finding it for me :-)  I am pretty much self taught and have had a 10 year hiatus thanks to children etc, so i've just started again.  Previously i had been working with cone 8 - 10 glazes and although it took me a while of experimenting i found a few glazes that worked really well for me.   Someone once told me that soaking at the top temperature was a good idea for pinholing - i tried it and it appeared to work.  However since then i've been experimenting with cone 6 and i'm really disappointed with the results.  I'm thinking of going back to high temp glazes.  Too glossy, lots of pin-holing :-(

However research i've been doing has suggested using controlled cooling may help with the problems i've been having and i thought i'd ask the community for their thoughts on the matter.  

thank you

 

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There is a fire down protocol that is far more successful with pin holes so I am familiar with your research.. Soaking at the top, not so much success for several technical reasons even though it seems intuitive.. Your cone six glazes should work well once you find compatible ones. The Glazy link is good here, double checked but you can search recipe 19734 and that should  do it.

just curious, do you fire with witness cones to verify? 

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11 hours ago, EKasse said:

It's the TC1800 - http://www.rlkilnservices.co.uk/controller_manuals/Studio 1800 Manual.pdf - i've just had another read through the manual and can't work out if i can slow the cooling with this controller.  i'm pretty sure i can't.  i would be delighted if i could be told otherwise!

Looking at the manual for the IPCO 3000 programmer https://www.potclays.co.uk/studio/files/cms/pages/downloads/controllers/download-list-files-8867.pdf?nocache=20180917045822, and comparing the two, I'd say the 1800 only has one programme and one ramp :-(  

I think you shpuld be able to start a new programme straight after the first one has finished, and set a rate = to cooling degrees per hour, and target temperature being when you're happy for it to cool naturally.

So, heating might be 150C/hour, to 1200, soak 10.

Cooling might be 50C/hour, to 500, soak 0/10/? 

 

Or if you can afford it, buy a new controller with more programmes and more ramps.

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