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Second bisque firing

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123pop    2

Second time bisque firing. Do you all wait until all moisture (seen on mirror held to peephole) stops before turning up to high?? I didn't see any moisture at low (held for 4 hours) then when I get to med ( top and bottom dials), it is fogging the mirror plenty. First time I just waited until it stopped about 3-4 hrs on med. Is this the correct procedure???.

Thanks this is so exciting.

I have a Cress kiln sitter Kiln with just the two dials and 2 peepholes.

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Marcia Selsor    1,301

I would leave the lid cracked an inch. Fire 2 hours on low, then 2 hours on med. then shut the lid and turn the kiln to high. This schedule is for dried pieces. If it is damp, put one switch on low over night to force dry with the lid slightly open.

 

Marcia

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Bob Coyle    113

Thanks..... so the water vapor on the mirror really doesn't matter?

 

 

Yes it does. This is water of hydration coming out at around 1200 F. The clay is undergoing a chemical change and if you push the temperature up too fast you may get a blow. I never go to the high range until the the mirror is not showing steaming... or at least not showing heavy steaming.

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Marcia Selsor    1,301

The water vapor does matter as I said. The pots need to be dry. That is the schedule I used for over 25 years of firing at the University. But don't shut the lid it if you have water vapor.

Montana is a dry place. I didn't have any problems with that schedule.

 

Marcia

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OffCenter    82

If the pots are DRY and they are not extra thick (like in sculpture), then you're just wasting time and electricity by looking at mirrors and worrying about the chemical water. Just fire with lid closed and all peeps in (or leave the top one out for the whole firing) on low until you are well past boiling say 250 degrees F. then turn the kiln on high. That's the "schedule" I've always used and use now in 3 different elect kilns (each a different size and manufacturer) to bisque and my pots don't blow up. Basically, what Marcia said except I probably turn on high after about 2 1/2 to 3 hrs instead of 4 depending on how full the kiln is and how big the biggest pot is.

 

Jim

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Chris Campbell    1,088

I agree with Jim ... Been potting for a lot of years and have never held a mirror up to a kiln to check for steam or vapor.

If you put your pots on your cheek and they don't feel cool, they are usually dry enough to fire ... unless the pots are super thick, children's work or sculpture.

I wonder if this super concern for dryness comes from communal spaces where the person in charge of firings wants no blame so insists on every pot being incredibly dry

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123pop    2

I guess what is confusing is ?? the water from a not dry pot is different than the water vapor coming out later when really heating up???

There is no way these pots were not dry since I candled them also.

Just trying to understand what is going on in the kiln. No steam on mirror at all on low... but literally wet at med???

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Pres    896

I guess what is confusing is ?? the water from a not dry pot is different than the water vapor coming out later when really heating up???

There is no way these pots were not dry since I candled them also.

Just trying to understand what is going on in the kiln. No steam on mirror at all on low... but literally wet at med???

 

Remember that there are basically three types of water occurring in your pots. Mechanical water-making the clay pliable, which evaporates as the pot dries. Atmospheric water-basically the dryness the pot will get depending on humidity or your pot will get no drier than the humidity of the day. Chemical water-part of the clay formula that breaks down during firing. In most firings you will have moisture during the water smoking(lid cracked, plugs out, switches at low)this is basically the atmospheric water leaving the pot, then up to 1100F @ you will have the chemical water changes.

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Frederik-W    23

I agree with Jim. Don't waste time, electricity & generate unecessary greenhouse gas.

Let the sun dry your stuff when you can, then fire them as quick as you can - bearing in mind thick or uneven pieces.

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Second time bisque firing. Do you all wait until all moisture (seen on mirror held to peephole) stops before turning up to high?? I didn't see any moisture at low (held for 4 hours) then when I get to med ( top and bottom dials), it is fogging the mirror plenty. First time I just waited until it stopped about 3-4 hrs on med. Is this the correct procedure???.

 

"Second time bisque firing"--does this mean you are firing greenware (the raw clay), or is this a glaze firing?

 

Sincerely,

 

Arnold Howard

Paragon Industries, L.P., Mesquite, Texas USA

ahoward@paragonweb.com / www.paragonweb.com

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