Single Firing in the Cone 5 - 7 Range

Why Single Fire?

  • Have you ever been caught up in a rush of creative energy while shaping a piece, and lost that feeling while you waited for the piece to dry and then be bisque fired?
  • When you look at the bisqued piece, does in seem lifeless and divorced from when you were shaping it? Does it feel like glazing is some totally separate process that is very difficult to unify with the forming process?
  • Do you hate the way bisqueware sucks the liquid out of your glazes, making runs and drips twice as thick as the rest of the glaze coating? And when you do brushwork does this sucking property thwart your attempts at carefully controlled strokes?
  • Do your high clay content glazes shrink and crack on bisqueware and then crawl away from the cracks in the firing?
  • Do you love the feel and control of painting with acrylics or oils where your paint glides off the brush and mixes predictably with previous strokes?
  • Would you like to compress your production cycle into half your usual time?
  • Would you like to use about a third less energy in firing your kiln?
  • Would you like to cut your kiln loading and unloading in half, while still producing the same amount of finished work?

The more of those questions to which you answered "Yes", the more reasons for you to look into single firing.

George Lewter from cone6pots.ning.com has started a single fire interest group. If we can get a committed group together to study the single fire process somewhat systematically, we will likely progress much faster than if we work individually in isolation. With a dedicated group we would also have a better chance of enlisting the aid of one or more established experts.

  • For a preview of why you might want to do something so radical, see the electric glaze firing page at centerstreetclay.com Steven Hill's Website. He has been single firing for some thirty years.
  • Basically, single firing involves glazing your pieces when they are in the leather hard to bone dry stage. You need to use high clay content glazes that will shrink similarly to the clay body to which they are applied as both the body and glaze dry out. Firing has to be very slow in the initial phases to allow moisture to escape slowly from the body and through the glaze without separating the two. After the unbound water and the water of crystalization are driven off, the rest of the firing cycle can proceed pretty normally for the glaze effects you are trying to achieve.
  • Single firing is not some Johnnie-Come-Lately, hare-brained invention. It has been used commercially for many years, glazed bricks, roof, floor, and wall tiles, toilets, and ceramic plumbing fixtures are all typically single fired.

Here are some links to photographs of single fired pottery.

  • These are gorgeous pots by Gertrude Graham Smith.  They were salt fired to cone 10, so we won't be able to duplicate this look in our cone 6 oxidation firing.  This is just a sampling of possibilities.
  • I received an email from Ellen Fisher as to her firing range, and she's doing low fire terra cotta, single firing with commercial low-fire glazes. So the technique is valid across all clay firing temperatures.

If you are ready to dive in then you'll need some techniques.  You won't be able to use those glazing tongs on leather hard clay or on greenware.

  • Richard Aerni had an article on single firing in the Dec 94 issue of Ceramics Monthly which you can read at his Website. He's talking about ash glazes reduction fired to cone 10, but his discussion of glaze mixing, combinations, and spray application apply equally to our work at cone 6 in oxidation. 

  • An Obvious Combination for Single Firing

    would be to paint a leatherhard piece with colored slips, and then glaze it with a suitable clear single fire glaze. I haven't found a lot of ^6 raw glazes, but here are a couple quoted from the clayart listserve.

    Marek & Pauline Drzazga-Donaldson on fri 10 mar 00

    I have developed a once fire cone 6 glaze from the basic Leach cone 10 - 11 glaze.

    Cone 6 Based on Leach Clear/Transparent Oxidised
    Potash Feldspar 40
    Flint (Quartz) 25
    Whiting (CaCo3) 20
    China Clay 12.5
    This gives a really good shiny surface and can be quite thick and does not run. You could add 2.5 of Bentonite to make it up to unity.

    Cone 6 Raw or Once Fired Glaze. This glaze can be painted on very easily.
    Potash Feldspar 38
    Flint (Quartz) 20
    Whiting (Chalk) 32
    Ball Clay 10
    Bentonite 2
    This glaze acts in similar manner to the first. Can be applied thick, takes oxides well, very stable over a wide range, does not run. If this one works for you let me know. It really is a stallwart for me.If you give it a really good cone 6 -7 then it will pool nicely. Happy potting Marek http://www.moley.uk.com

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Comment by Diane Stirling on November 16, 2016 at 6:08am

Thanks for sharing. Marek and Pauline.  I am going to try these. The cost of firing these days is so expensive and of course people don't want to pay the price that we deserve so we need to work out every way we can to reduce our time and cost of firing. 

Comment by Tom Humphries on April 25, 2015 at 5:29pm
Can anyone give more specifics about what 'high clay content' glazes means? Is there a certain ratio that needs to be met? I'm currently using glossy G1214W and matt G1214Z as bases and wondered if they would be suitable for once firing, or maybe its just a case of trial and error?
Comment by Norm Stuart on May 29, 2014 at 3:54pm

Firing bisque to a hotter cone like Cone 03, rather than a Cone 04 or 05, will eliminate excess porosity which causes these problems.

At our studio, excessively porous bisque tends to give people the perception that they've applied far less glaze than they have.  As the clay body densifies at Cone 6, the result is a piece with a large excess of glaze and runs as the glaze is essentially wrung from the immature and excessively porous bisque.

  • Do you hate the way bisqueware sucks the liquid out of your glazes, making runs and drips twice as thick as the rest of the glaze coating? And when you do brushwork does this sucking property thwart your attempts at carefully controlled strokes?
  • Do you love the feel and control of painting with acrylics or oils where your paint glides off the brush and mixes predictably with previous strokes?
Comment by susan claysmith on May 28, 2014 at 11:24pm

Hey these are pretty nice! Are those stained glass inserts in clay shades?

Comment by John Bowers on May 28, 2014 at 4:42pm

Hi I'm new to the group and to single fire. here are some photos of my latest work, June  to October 2013, all single fired.

Comment by Jan Wallace on December 1, 2012 at 3:03am

Hi everyone. I Single fired a kiln load of Xmas Dec's using the same clay for entire kiln load of pieces (small kiln). Fired an earthenware clay to 1100c (no soak at 1100c) using a commercial clear over u/glaze dec. I just started using a new 'snow white e/w clay'. I have never had this issue ever before. The bottom shelf of dec's all shivered and glaze flaking off all pieces. Rest of kiln was okay. Any comments about this would be appreciated. I understand about shivering but not why only happened on the bottom shelf. Bottom shelf of my kiln fires a little cooler than the rest and cools quicker. Perhaps a temp variation? What do you think?

Comment by George Lewter on April 24, 2011 at 8:02pm

SH = Steven Hill 

  • Strontium Crystal Magic
  • Hannah's Fake Ash (brown, blue, and green)
  • Water Color (Blue and Green)
  • 2-D Blue
  • Spotted Black
  • Pier Black
  • Jen's Juicy Fruit

You can find the above recipes on the Lakeside Pottery glaze page, and elsewhere on the Internet. Just Google the glaze names. Some will say Cone 10 or reduction, but most of them will work at cone 6 oxidation when you layer them on top of each other and some work just fine by themselves at cone 6.

Comment by susan claysmith on April 24, 2011 at 7:11pm
Hey George - What are SH glazes?? Thanks, Susan
Comment by George Lewter on April 24, 2011 at 7:09pm
Raw glazing today with SH glazes plus Nutmeg, Variegated Slate Blue, and C Harris Temoku. Planning to mix up a few more tests before stacking and firing with my new kiln controller.
Comment by susan claysmith on December 11, 2010 at 3:03am

SIngle fired tiles and Sushi sets.

Comment by susan claysmith on December 11, 2010 at 2:44am

My latest products of single firing using the Mishima technique.

SIngle fired Mishima tiles.

Comment by susan claysmith on December 7, 2010 at 4:56pm
Hi George - I hadn't put much time into these pieces, but I am totally happy with how they cam out. I'm not sure that they would have looked any different had I bisqued them first. I am fully inspired to do more. I mad a Sushi set the other night and am going to single fire it with my next gaze firing and I am going to throw some smaller pieces such as cups to try as well.
Comment by George Lewter on December 7, 2010 at 3:00pm
So, Susan, what do you think of the results? Did your pieces come out differently than if you had glazed them as bisqueware? To me they appear pretty nice,without obvious defects.
Comment by susan claysmith on December 7, 2010 at 3:27am
I have just made my first attempts at single firing. I had mad a bunch of sushi plates that that I decided to glaze raw with a few of my existing glazes that had a high clay content. The glazes were brushed on with a very wide brush, and they were fired with kiln full of ware that had been previously bisqued. I treated the first part of the firing like a bisque firing and the reat like I would normally fire a glaze firing.
Here are a few results.

Comment by Robert Young on September 12, 2009 at 11:58am
I am eager to try a few pieces as well...

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