Tell us how you fire

[Chris Campbell]

Many of us were taught "rules" about firing ... such as bisque low, fire high ... or "ALWAYS" do this or that when in truth there are a numerous ways to fire and as with almost everything in clay, it all depends.

Maybe if some of us share our various firing methods we can soften the rule of bisque at 06, fire at 6.

 

If I bisque at all, it is to cone 018 so the ware is soft enough to sand ... Colored clay patterns sometimes get smudged and need this cleaning which is safer to do on bisque than on thin greenware. If I don't need to sand anything, I once fire high. If I need any clear glaze, that follows at 04.

Raku ware only gets bisqued to 08 so the clay body stays open.

Pieces that I decorate with underglaze will sometimes be fired to 018 multiple times between color applications.

 

What do you all do that is different?

[DAY]

First off, I am not a potter- just an artist who works in clay instead of paint or wood or poetry. 25 years ago I developed my "look" of leaves on clay, colored with Velvet Underglazes, oxides, and the occasional pinch of magical elixirs. I single fire my cone 5-6 (Standard Ceramics) stoneware to cone 1.

So far, it has worked.

 

 

[yedrow]

Wow Chris, I just checked out your website and you are awesome! Your work greatly transcends the medium.

 

I'm afraid I only recently began working with glazes so I have nothing to contribute.

 

I've wondered though if the options for single fired glazes were limited because most glazes have an expansion rate that matches twice fired ware. Hmm, come to think of it, I'm not sure why that would be.

[scoobydoozie]

Great topic, Chris! And there's lots to learn. Chris, is this strictly your guidelines for porcelain and what recommended cone of clay? I assume if you are glaze firing to 04 that it is a low fire clear glaze? I'm new and didn't realize you could use low fire glaze on a high fired body. I would have thought it would craze or something.... I assumed the glaze needed to match the top temperatur the body was fired to....

 

If I may ask, would everyone include with their reply the type of clay and if your firing process applies to all types and cones of clay or is different for each?

[scoobydoozie]

Great topic, Chris! And there's lots to learn. Chris, is this strictly your guidelines for porcelain and what recommended cone of clay? I assume if you are glaze firing to 04 that it is a low fire clear glaze? I'm new and didn't realize you could use low fire glaze on a high fired body. I would have thought it would craze or something.... I assumed the glaze needed to be closer to the top temperature the body was fired to?

 

If I may ask, would everyone include with their reply the type of clay and if your firing process applies to all types and cones of clay or is different for each?

 

[Matt Oz]

I decided clay slumping during firing is not necessarily a bad thing.

 

 

 

[Chris Campbell]

I have always found it difficult to get good information on firing porcelain ... Most books are so vague that it almost makes it worse rather than better. I got Southern Ice at the first NCECA where free samples were offered and have been using it ever since ... Don't know how many years? I honestly still don't know if I am doing it right or not but over the years my process has certainly evolved ... with and without accurate help.

 

I support all my pieces in forms made with a more durable high firing clay or with castable refractories. Porcelain slumps at high temps so you gotta give it support.

I very seldom do, but if I am making wares for functional use I will glaze the top surface with a high firing clear glaze during that firing. Since it is supported, there is no way to glaze the bottom at high temps. That is why I would need a second firing at a lower temp that will not cause any slumping or warping. If I am only glazing for artistic effect, I don't really care about fit and I have found my Amaco commercial clears to be extremely forgiving.

 

Right now I have a load of Cone 9 going through the controlled cooling phase of the firing. Controlled cooling is the best thing you can do for your work. A lot of firing problems occur on the way down, not up. My instances of warping and cracking dropped dramatically when I began to follow this cooling method.

Why Cone 9 instead of 10 ... Because I personally cannot see any difference in the end product so why fire higher?

[Guest JBaymore]

One of the key concepts that I stress in the kiln design and operation courses/workshops I teach is that there is no such thing as a one-size-fits-all "cookbook" firing schedule. That developing the best firing profile for a given situation involves developing it specifically for the clay body(s), the glaze(s), and characteristics of the particular kiln unit.

 

That firing schedule you "used in school" is not necessarily the "right" one for your new kiln, new clay body, or new glazes. Firing shcedules others use are for gathering ideas and broad concepts .... not for exact solutions.

 

If you understand what is happening IN a firing to the ceramic materials, and how combustion, heat transfer, and chemical reactions take place in a kiln... then your hands are completely untied from all of the "rules" and the "do it this way or else" BS that floats around the ceramic community.

 

Then the "rules" that you are left with are based in what amounts to physical and materials science..... and those core rules are the ones that can't really be messed with. For example...... no matter what you do in a kiln, heat energy will not move from areas of lower concentration to areas of higher concentration (a basic concept from the Laws of Thermodynamics).

 

best,

 

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

[Christine]

First off, I am not a potter- just an artist who works in clay instead of paint or wood or poetry. 25 years ago I developed my "look" of leaves on clay, colored with Velvet Underglazes, oxides, and the occasional pinch of magical elixirs. I single fire my cone 5-6 (Standard Ceramics) stoneware to cone 1.

So far, it has worked.

 

 

 

 

 

.... so disappointed not to be able to follow the link you posted to your work - could you perhaps post pictures?

 

Christine

[Karen B]

I love the surfaces of your work Chris!

[DAY]

First off, I am not a potter- just an artist who works in clay instead of paint or wood or poetry. 25 years ago I developed my "look" of leaves on clay, colored with Velvet Underglazes, oxides, and the occasional pinch of magical elixirs. I single fire my cone 5-6 (Standard Ceramics) stoneware to cone 1.

So far, it has worked.

 

 

 

 

 

.... so disappointed not to be able to follow the link you posted to your work - could you perhaps post pictures?

 

Christine

 

 

Sorry, 'bout that- copy/paste works elsewhere. He's my retail website: www.steve-day.com

[yedrow]

If you understand what is happening IN a firing to the ceramic materials, and how combustion, heat transfer, and chemical reactions take place in a kiln... then your hands are completely untied from all of the "rules" and the "do it this way or else" BS that floats around the ceramic community.

 

I'm entering glazing with exactly this philosophy. If the process is understood it ceases to be voodoo. I've known too many potters that follow odd 'rules' in place of good science.

 

Oh yea, I too slow the cooling in my electric kiln for a couple of hours.

 

I have a Bulgarian friend who also does multiple firings with glazes that fire to different temps. I'm trying to figure out that process as I look into the art of the many ways of layering glazes. Thanks again Chris, for the inspiration.

 

 

 

[TheSmartCat]

I work in terra cotta majolica, almost the opposite end of the firing range from you, Chris. Most of my work is bisqued and glazed at ^04....and yes, I fire them together, usually on different shelves. By firing my bisque to glaze temp I assure that the pot will be stable when I do my glaze design. One interesting thing I have found is that I can once fire with a commercial glaze. With my own studio glazes once firing is a disaster.

 

I have a Bailey 7 cu. ft. electric kiln with a blank ring on the top. As long as I have one ring of elements above the shelf the blank ring goes up to temp. After a lot of experimentation I have found that the preset ^04 cycle is the best for firing my work. When I used to fire with a friend, in a much smaller kiln, I found that I had to do a ten minute soak and an extremely slow cool-down. All this has taught me that every kiln is different and needs to be tested before firing favorite work.

[Lucille Oka]

Beginning potters need rules. It is a starting point to give them some assurance of success. Later when they become more familiar with the testing of the clays, the different techniques, the glazes, and the kiln, etc., they can make changes if they want; just as we all have done.

 

[TheSmartCat]

Beginning potters need rules. It is a starting point to give them some assurance of success. Later when they become more familiar with the testing of the clays, the different techniques, the glazes, and the kiln, etc., they can make changes if they want; just as we all have done.

 

 

I totally agree with you, Lucille. When I was teaching I made sure the rules or guides were completely understood. Once that was achieved I encouraged pushing to the point of collapse, especially in designing and making work. I have always felt that you cannot discover what clay can do if you don't discover what it can't do.

[Chris Campbell]

Beginning potters need rules. It is a starting point to give them some assurance of success. Later when they become more familiar with the testing of the clays, the different techniques, the glazes, and the kiln, etc., they can make changes if they want; just as we all have done.

 

 

I totally agree with you, Lucille. When I was teaching I made sure the rules or guides were completely understood. Once that was achieved I encouraged pushing to the point of collapse, especially in designing and making work. I have always felt that you cannot discover what clay can do if you don't discover what it can't do.

 

 

I agree that in order to prevent total chaos in teaching studios rules need to be set and followed. There is nothing wrong with this as it truly follows my favorite rule of " It all depends ..". What needs to be added however is the knowledge that these are the rules for this particular location and that there are other ways of doing things that they are free to discover in their own studios. Too often students are left with the idea that this is the only way, rather than the most orderly way for a classroom situation.

[Guest JBaymore]

What needs to be added however is the knowledge that these are the rules for this particular location and that there are other ways of doing things that they are free to discover in their own studios. Too often students are left with the idea that this is the only way, rather than the most orderly way for a classroom situation.

 

Ye verrily!!!!!! and Amen.

 

best,

 

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

[Karen B]

I fire terra cotta hotter than 04. It makes for a rich brown color.

[Red Rocks]

I have always found it difficult to get good information on firing porcelain ... Most books are so vague that it almost makes it worse rather than better. I got Southern Ice at the first NCECA where free samples were offered and have been using it ever since ... Don't know how many years? I honestly still don't know if I am doing it right or not but over the years my process has certainly evolved ... with and without accurate help.

 

I support all my pieces in forms made with a more durable high firing clay or with castable refractories. Porcelain slumps at high temps so you gotta give it support.

I very seldom do, but if I am making wares for functional use I will glaze the top surface with a high firing clear glaze during that firing. Since it is supported, there is no way to glaze the bottom at high temps. That is why I would need a second firing at a lower temp that will not cause any slumping or warping. If I am only glazing for artistic effect, I don't really care about fit and I have found my Amaco commercial clears to be extremely forgiving.

 

Right now I have a load of Cone 9 going through the controlled cooling phase of the firing. Controlled cooling is the best thing you can do for your work. A lot of firing problems occur on the way down, not up. My instances of warping and cracking dropped dramatically when I began to follow this cooling method.

Why Cone 9 instead of 10 ... Because I personally cannot see any difference in the end product so why fire higher?

 

[Red Rocks]

I have always found it difficult to get good information on firing porcelain ... Most books are so vague that it almost makes it worse rather than better. I got Southern Ice at the first NCECA where free samples were offered and have been using it ever since ... Don't know how many years? I honestly still don't know if I am doing it right or not but over the years my process has certainly evolved ... with and without accurate help.

 

I support all my pieces in forms made with a more durable high firing clay or with castable refractories. Porcelain slumps at high temps so you gotta give it support.

I very seldom do, but if I am making wares for functional use I will glaze the top surface with a high firing clear glaze during that firing. Since it is supported, there is no way to glaze the bottom at high temps. That is why I would need a second firing at a lower temp that will not cause any slumping or warping. If I am only glazing for artistic effect, I don't really care about fit and I have found my Amaco commercial clears to be extremely forgiving.

 

Right now I have a load of Cone 9 going through the controlled cooling phase of the firing. Controlled cooling is the best thing you can do for your work. A lot of firing problems occur on the way down, not up. My instances of warping and cracking dropped dramatically when I began to follow this cooling method.

Why Cone 9 instead of 10 ... Because I personally cannot see any difference in the end product so why fire higher?

 

 

 

Hi Chris:

 

Great topic. Can you please clarify that you fire all of your pieces in formsto keep them from slumping? That is what I thought I read in your last post.This would seem to double the amount of ware that you have to heat in everyfiring. Is this the only way to keep your elegant forms from slumping? Also why don’t the forms slump?

 

Also, can you expand on what you mean on controlled cooling? We fire to Cone 10in a gas kiln and let it cool naturally without any noticeable incidents ofwarping or cracking. I would be very interested though in knowing more aboutyour process and how you arrived at it.

 

 

Thanks,,,,

 

[Chris Campbell]

Because porcelain has no grog, it slumps and warps at high temps. Any form that spreads out from center ... like a bowl ... needs to be supported or it will sag. The support forms are made from a hardier, grogged clay that can withstand temps higher than my firing temp, so I am not pushing it to its limits at cone 9. The pieces dry in the form and fired in the form.

 

If you use gas, I don't think you need controlled cooling ... it's mostly for electric kilns that cool much too quickly because of the thinner walls .... If this is wrong, someone please jump in!

[OffCenter]

no matter what you do in a kiln, heat energy will not move from areas of lower concentration to areas of higher concentration (a basic concept from the Laws of Thermodynamics).

 

 

For those of us who sometimes have trouble with the law, you're not talking about a higher concentration of mass (pots, shelves, etc.) but a higher concentration of heat or, in other words, hotter area of the kiln, right?

 

Jim

[OffCenter]

A while back I made someone here mad because they thought I was insulting one of my favorite potters, Steven Hill, when I said that sometimes you can get the same results or even better results by firing one cone hotter instead of using a complicated controlled cooling cycle. In my case, I was using a rather complicated firing program with lots of holds and slow ramps down for some cone 6 electric firings, but then, just before a show, my computer controlled kiln broke down and I had to fire in the kiln I usually just bisqued in that has no computer. But I fired to cone 7 instead of 6 and the glazes came out just as nice. Heat work is what is important and there's more than one way to get the same amount. Now, I save lots of time and wear and tear on my kilns by firing a little higher than recommended instead of controlling the cooling. Note that I'm not saying this works for all glazes, just for a lot of them (like many of Steven Hill's glazes that need time to form crystals).

 

Jim

[Guest JBaymore]

no matter what you do in a kiln, heat energy will not move from areas of lower concentration to areas of higher concentration (a basic concept from the Laws of Thermodynamics).

 

 

For those of us who sometimes have trouble with the law, you're not talking about a higher concentration of mass (pots, shelves, etc.) but a higher concentration of heat or, in other words, hotter area of the kiln, right?

 

Jim

 

 

Jim,

 

Think of it like water flowing downhill. Water does not flow uphill unassited.... you need a pump for that. (A heat pump is used for making heat energy go "uphill" . )

 

Does that help?

 

Potter type example: If I have an uneven kiln chamber, and one area is hotter than another area........ if I can "stall" the climb of the hotter area, and get the total heat input into the kiln chamber to equal ALL of the losses from that chamber, the hotter part of the kiln will get cooler and the colder part will get hotter until they reach a stage of equilibrium (even temperature distribution) whre it is equal in temperature everywhere.

 

best,

 

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

[OffCenter]

no matter what you do in a kiln, heat energy will not move from areas of lower concentration to areas of higher concentration (a basic concept from the Laws of Thermodynamics).

 

 

For those of us who sometimes have trouble with the law, you're not talking about a higher concentration of mass (pots, shelves, etc.) but a higher concentration of heat or, in other words, hotter area of the kiln, right?

 

Jim

 

 

Jim,

 

Think of it like water flowing downhill. Water does not flow uphill unassited.... you need a pump for that. (A heat pump is used for making heat energy go "uphill" . )

 

Does that help?

 

Potter type example: If I have an uneven kiln chamber, and one area is hotter than another area........ if I can "stall" the climb of the hotter area, and get the total heat input into the kiln chamber to equal ALL of the losses from that chamber, the hotter part of the kiln will get cooler and the colder part will get hotter until they reach a stage of equilibrium (even temperature distribution) whre it is equal in temperature everywhere.

 

best,

 

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

 

 

Got it. Thanks. Just wanted to make sure you were talking about heat not mass. (btw, water doesn't flow downhill unassisted, either, you need gravity for that.)

 

Jim