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Stephen

Really Pushing It And Not Having Problems

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Had an out of town show this weekend and was faced with a last load I absolutely wanted to bring. The way it all worked out with drive time the kiln had to be unloaded and packed by 10am. The only way I could accomplish this was to use fast firing setting on my skutt 1027. Medium fire takes 8.5 hours and then 13 hours to cool (thanks to 3" bricks)  below 350 to prop lid and 250 to open lid. I usually let cool to under 200 to prop and 150 to open lid and unload BUT I was pushing everything as I even candled 40 same day handled leather hard mugs for bisque load for 10 hours to get it to this point. Usually rack under plastic for a day after handling then dry for one even when rushing.

 

So to re-cap, 50 mugs, 40 of them handled just as dry enough to work with with and not warp from handling, candled at leather hard (barely) and then cone 5 fast fired glazed with 20 minute hold in 4.5 hours and lid propped at 350, lid opened at 250 and unloaded at 190ish.

 

I didn't lose one mug. No cracks or glaze defects, none.

 

I used to have a 1027 for bisque and a 9cf oval for glazing and could move stuff through working in tandem bisque/glaze. Now with this one small 6.5 kiln there just isn't enough hours in a day to push loads through and add to that the 3" bricks adding hours to cooling it can take almost three days to push a load through.

 

So I'm so tempted to start relying on fast fire glaze and propping at 350 on a regular basis. Cuts 6-7 hours from the process. Was I just lucky or are people just being overly cautious with the more moderate and best practices approach. I've surfed and opinions seem all over the board and I have seen pictures of what is supposed to be evidence but I am wondering if the defects are really more attributable to other issues like glaze fit and the cautious approach just makes those issues less severe. I know I saw the same warnings on candling yet I have not had any issues with doing that either and have now moved 100s through candling 8-10 hours of sometimes almost wet pots without any issues.  

 

I should mention I can't afford a 2nd kiln right now and just paid 3 grand for this one so can't upgrade. Now I wish I had bought 2 used ones but can't undo that decision :-) 

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You have to push to find the limits-once you realize what you can do with the particular clay body  you use and climate you live in and firing cycle you are doing you can find many of the preconceived ideas do not hold water anymore. I will add at some point you will find the wall and have to back down the speed-weather drying handling or firing or cooling .

I think most in ceramics baby the work but they can afford to as its not a living. We you find the limits are not where you thought  and you will move into another level of production and realize what may be possible .This also applies to other processes as well.

Just when you have it figured out is when the c ceramic gods step in and crush you with a ruined load or bad glaze or bad clay or 10,000 other issues that go sideways-it the nature of ceramics.

Chris Campbell and preeta like this

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yeah I would have been bummed if the whole load had been ruined but knew going in that it might not work. I was actually just hoping half would make it through. Its a new style and really wanted to test at this market. Very surprised they all made it. Taking them was actually more important to me than the pots themselves.

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I agree 100% with Mark.

Most firing schedules I read about here are slow and conservative ... fine if every piece is precious, but production wise it just does not work. Not all clay bodies are so fussy they cannot be rushed ... some are, but not all.

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If you try a load of platters or pots with a much larger base than mugs let us know what happens with a fast fire and cool. :unsure: Would be interesting to test the clay with the fast fire schedule and see if there is any difference with absorption /maturity between it and your regular firing schedule.

 

edit: also think you could run into problems with blowing through some temperatures with glazes and clay gassing out.

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If you look at what industry does with firing cycles... there is a lot to learn.

 

Some industrial "clay" bodies are certainly ceramic products when fired.... but contain little to no plastic clay.  Alumino-silicate materials.... but that pesky clay stuff causes problems.  ;)

 

best,

 

...................john

Chris Campbell likes this

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You can get away with a lot with small, thin pieces like mugs. Plates, platters, large bowls, lidded jars, etc, all absorb heat and cool down differently, so you may run into problems there. I usually open my kilns at 300F, often bisque fire on 'Fast Glaze' (4.5 hours), and put just pulled handles into the kiln for fast drying, and that's all with porcelain. The problem is not the speed at which things happen, it's the evenness at which things happen. I can't dry out just trimmed oil bottles in the kiln because they will S crack, because with closed forms the inside can't dry as quickly as the outside. I won't bisque fire a stack of plates on 'Fast Glaze' because some will crack since the middle of the stack won't heat as quickly as the edges. I won't fast glaze or fast cool a 15 pound lidded jar because it's thicker than a little mug and won't heat or cool as evenly. I'ts good to know that you can push some things when you need to, though.

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I am working in porcelain so will throw a couple of test platters and such and give the fast fire a try and report back as soon as I have the open kiln time to try it, In the meantime I will take the advice of keeping it to mugs and small stuff for fast fire. I do a lot of mugs so the fast fire will help a lot with keeping things moving.

 

My real bottleneck is having one small 6.5 cf kiln but this helps.

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stephen thanks for this question. i learnt so much from the question and answers. things i hadn't even thought about.

 I won't fast glaze or fast cool a 15 pound lidded jar because it's thicker than a little mug and won't heat or cool as evenly. 

Is that the reason why in kiln loads with mixed forms you see the bigger taller forms on the top shelf of a gas kiln (i noticed when looking at pictures of loaded kilns (mainly updraft gas kilns) the taller and bigger forms are placed on the top? i would imagine the top would be hotter. 

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