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clayshapes

single firing, cone 6 stoneware

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Hello,

I'm not a professionally trained potter -- I've been teaching myself through trial and error, and taking the odd class over the last year. I bought a used kiln and have had many adventures! Yesterday I was doing a glaze firing of some bisqued cone 6 stoneware pieces and I had a small greenware pinch pot of the same clay body that I'd forgotten to include in the bisque firing last week. I decided to glaze it as usual as an experiment to see what would happen if I skipped the bisque firing -- and then proceeded as usual for my glaze firing. The unbisqued piece appears to have come out exactly as it would have if it had been bisque fired first. It feels the same weight -- and the glazes behaved exactly the same as usual.This piece was glazed in the same glaze as a bisqued piece next to it in the kiln and their colour is identical.

So, my question is: what are the disadvantages of going straight to a glaze firing and skipping bisquing?

I can imagine that one hazard would be the effect that wet glaze could have on greenware -- especially a delicate thin piece -- there might be a risk of the clay disintegrating or cracking from the moisture. This didn't happen in this tiny experiment though (and I didn't even let it dry for long -- I glazed it at the last moment and just put it in the kiln and fired it up!)

I'd love to hear from properly trained potters about the disadvantage of simple single firing.

By the way - in case it is of interest in this matter: I have an old Duncan kiln that performs beautifully - although the kiln sitter does not work properly on a cone 6 firing (fine on cone 04 bisque firing) but I've gotten to know my kiln and it does a glaze firing in 6-7.5 hours. I watch the cones carefully and have had no problems.

Looking forward to hearing from the experts on this!

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Potters have "single fired" for several thousand years!<div><br><div>To learn more- everything!- google "steven hill single fire".</div></div>

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Clayshapes,

 

It's generally better to glaze the piece when it's leather hard, at least that is what the recommendations are that I have seen. I've done it a few times and like the way the items turn out. It's been a while since I've done any, but as soon as I get set up after our move I'm going to be making some bowls to single fire.

 

Bob

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Thanks for all the posts. I have some reading to do. I guess I'm just surprised that my very limited experiment had such good results. I'm wondering why I bother bisquing at all. But I'll read up and find out. Thanks again.

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I single fire whenever I can, I always singlefire flat pieces and everything that can be spray glazed, obviously it is difficult to dip glaze a bone dry piece...

Never had major problems, sometimes I got bubbles in the glaze (to fast fire, to thick glaze).

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So...what is the purpose of bisque firing first? I use commercial glazes, and brush them on (I do a lot of decorative work). Very curious about what the need for bisquing is! Have I just been wasting electricity all this time?

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the purpose of bisque fire in my opinion is to get sturdy pot which you can really hold (or even use glazing tongs- which I imagine are bad idea for bone dry pieces) and glaze without being afraid that it will crash into your glazing bucket. Bisque pot can get wet without being afraid that it will collapse.

If you are glazing bone dry piece you really have to be careful not to get too much water into it... so for example really thin porcelain cup cannot be glazed bone dry (at least with my skills) ;)

 

Anyway if I would brush my glazes on, I would choose single fire.

Stephen and Rae Reich like this

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Congratulations with trying and having success, and not blindly following accepted habits !!

 

I am very interested as well in single-firing and low temperatures- It saves electricity, saves the environment and saves time.

I think we can adapt techniques and glazes to accomodate single firing.

We should definitely not do bisque-firing simply because it is the accepted way of doing it.

E.g. bisque does make the work stronger to handle, but if we handle things more carefully then there is one reason less to do bisque,

another reason is that we do not always dip-glaze - we do not always have to.

I am very interested in other people's experiences with single-firing.

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Thanks for the encouragement. I have a new set of pieces ready for single firing. Can't wait to see how they turn out. I'm going to try it with earthenware clay too. Am prepared for disasters, but looking forward to the adventure!

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Like you Clayshapes, I am not a professionally trained potter, and my first foray into single-firing was adding a glazed greenware piece into a glaze firing. My excuse was I had a set of four porcelain bowls made and glazed and dropped one. So I made adjustments for shrinkage and threw another matching bowl, and let it dry, then glazed it. I put it in with the glazed group and ran my regular bisque fire schedule up to red heat, then proceed as usual for a glaze schedule. No problems! Its appearance when fired was slightly different than its three mates, but it was thrown separately, in addition to the glazing while greenware.

 

For my next foray into single firing, I fired a whole load of pots using the bisque up to red heat, then the glaze firing finish. No problems. I think the biggest issue may be firing out organic matter and having the escaping gas mess with your glaze. Going slow through certain heat ranges may help with that. I documented my first full single-fire load here:

 

http://wynhillpottery.weebly.com/single-fired-work-2010.html

 

My procedure for glazing is bone dry work, pour interiors on more closed forms, then spray the exterior right after. For open forms like bowls and platters, I spray the underside first then the top side. I admit that I still bisque then glaze most of the time, but my excuse is that I fire raku almost as much as regular glazed work, and single firing raku isn't going to work out.

 

John

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hi, am self taught for the last 40 years or so. i learned from lots of good OLDER books out there in my public library and lots of workshops. not everything is on the internet.

 

i have been single firing to cone 6 for years but i spray my glazes so it is easy to apply glaze to greenware.

 

the best reason for bisque firing that i can see is that if you want to scrub on underglaze colors or glazes into deep textures or any other technique which requires a lot of handling of the pot before putting it in the kiln. my latest work involves textured slabs formed into flowerpots or vases. spraying an interior glaze into a deep pot requires skill and is not always successful. i have dozen water-filled vases sitting on my work table right now. they have been there overnight to test their waterproof quality. one didn't make it because my spraying missed a small area near the bottom of a 7 inch deep vase. having poured the glaze into a bisqued vase would have avoided that one problem.

 

the strange thing you will eventually learn is that there are no absolutes in clay. someone's comment about bisque being stronger seems reasonable and i believe it. BUT. last week a phone call interrupted me while i was pouring glaze into a deep bisqued (to cone 04) vase. i got distracted and the vase was sitting there with a totally wet bottom half (6 inches) when i got back to it a few minutes later. after pouring out the glaze and finishing the exterior, i put it into the kiln. during the subsequent firing, it deformed in that area and the exterior glaze shivered off in a long, narrow section. go figure.

Rae Reich and ShellS like this

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All of these posts are so great! I'm really encouraged to keep experimenting. Thanks for all the advice, and for sharing your experiences with single firing. When I posted this I was afraid I'd get a lecture about doing things the established way. Glad to see there is a history to this, and a lot of other risk takers out there.

And "oldlady" (I don't like calling you that!!!) your comments about there being NO constants is well received. There are so many variables, as I have learned, often the hard way.

But in the end, it's only mud and water, isn't it? You can always try again. Although it never turns out the same, the next time!

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(I'd love to hear from properly trained potters about the disadvantage of simple single firing.)

I fit that description- One thing I should say first if whatever works for you than by all means do that-There is no right or wrong with clay. Some things are easier or harder.

As far a single firing from my point is its a slower glazing process with some risk of loss it lends itself to spraying the outsides. As a production potter I am all about the speed of production-we wax with a sponge (I can cover this later as well as hot dipping paraffin) The glazes are brushed and dipped not sprayed which is a slower process.So on speed and loss I'm bisquing. But if speed and efficiency do not matter by all means single fire this will be true for many hobby potters. Our USA salt history of pottery is all single fired and it works well on liner glazes. I single fire some salt wares myself. But of all the production potters I know in my art world none single fire. A few other considerations are stacking bisque ware for storage -with green pots this is limited. I stack bisque a mile high and stockpile it. Breakage is nil. Green ware is fragile so loss happens.

Hope that helped-I do many unconventional things and I think there are no rules is a good one.

Mark

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yep, stacking is important...

 

 

q: MarK C, can you tell more about sponge waxing and parafine dipping?

 

Is this pure parafine? mixed with wax? I have seen parafine dipping on youtube and it seems so easy ;)

 

which pots do you dip and which get sponged?

 

thanks

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Thanks for sharing those thoughts Mark. I can see the disadvantage for a studio potter - and for dippers.

I just made a whole whack of pendants -- I can see how they are perfectly suited to single firing -- they are flat, and can be brushed easily and quickly. I'm also going to single fire a whole kiln load of small pinch pots - the kind I sell as salt cellars. I'll glaze them at the leather hard stage. We'll see what happens. I'll have the usual trepidation opening the kiln!

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I single fire most of my work. I dip or pour the glaze on large pieces and have very little losses today but while learning I lost alot since my teachers didn't know much about it.

 

With simple glaze work I feel that I could be a raw ware production potter but It would effect shapes and workflow. I belive I would save time equal to the bisque. I think you can raw glaze most things if you get the timings and techniqe right but that takes time to learn. Another problem is the need to dry the pieces evenly, before dipping and after as glazes tend to flake if they dry to fast in the stage when the pot changes color; this will take some extra managing if you don't make some special drying space - not to dry, not to cold. But it seems like you have a super glaze there.

 

Another feature is that I can rawglaze my work at home, bisque it (!) and trasport it, glazed, trouble free. (I use a lot of different kiln over the country.)

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Hi

 

I have done single fire twice now. Seems to work great. Got the idea at one of Steven Hill's workshops.

 

Only problem so far... pieces break while glazing .... need extra care due to fragile nature of the dried raw clay.

 

As far as the firing itself - There is a low candling at first then ramp it up. I think there is a ramp setting on Hills web site. I modified it for my glaze. If you would like my temps and time let me know

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I spent several years making ^10 stoneware tiles for my garden, and successfully single-fired nearly all of them.

 

In my opinion, the major risk with not bisque-firing is having moisture trapped in a glazed greenware piece and having it blow up in the kiln. That can ruin an entire load, and also be really hard on the kiln. However, if you're careful to vent any enclosed sections of your pieces and thoroughly dry your work, that shouldn't be an issue.

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I single fire about half my work now. I am working carefully toward being 100% single fired in the near future. Not me, my pots... I have read Steven Hill's articles, and talked to a lot of potters. I find if I handle the pots carefully (a lot of my pieces are very thin stoneware bowls and very large bowls) The only breakage I have experienced so far is one bowl shattered when I dropped a 5/8 inch half shelf on it. I don't think the poor bowl would have had much of a chance surviving that, even if it had been bisqued.

 

I pour the insides of the pots and spray the outsides. I find the time (and energy - both electrical and personal) saved through eliminating bisque firing is well worth the extra care necessary in handling the pots. And I agree with StefanAnderson - if you're into heavy production, you might not want to risk the possible breakage. I am converted, just working carefully so I don't run into problems.

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I work in porcelain jewelry and we 50/50 bisque fire/single fire.

 

It depends on the detail of the work for us.

 

I have found that doing single fire on highly detailed (fine carving etc) tends to take away from the texture little bit. Also a benefit to doing a bisque fire is that if you mess up your piece while painting it you can simply wash the piece and start over. We do a lot of highly detailed work so it's beneficial to do a bisque for us.

 

Single firings are great when the piece is less detailed and I just want the glaze to do the talking.

 

So pros and cons for both.. Just have fun with it!

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Thanks for all the comments on single firing - but no-one has mentioned either the firing schedule they use OR whether they use their normal glazes (I fire to Cone 6) I am assuming you may need a much lower temperature glaze to achieve a "glazed" effect.  I was thinking of single firing some stoneware pieces for the garden and brushing on earthenware glaze. Can anyone see any potential problems? Also (so many questions!) will single fire, say up to 1000 degrees centigrade, still allow the stoneware clay to vitrify? And must it be fully vitrified for use as a planter pot?? All comments and suggestions gratefully received!

Edited by jacqui sos

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I don't know much about the details but when you single fire, you need to fire up to your clay's vitrification temperature. 

If you throw porcelain, your firing will need to be around 1250°C (or whatever you usually fire at). So earthenware glazes would finitely not withstand such temperature. If you underfire, I guess your glazes might vitrify but the clay won't mature leaving you with a very fragile pieces (especially if the bottom is unglazed and water gets in there as you use your pot)

I also wonder if there would me some mismatch in terms of shrinkage rate between your clay and your glazes...

But basically single-firing is skipping the bisque firing. So the firing you do should be your regular firing 

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1000 C is only ^05 (low fire)  so that is not going to vitrify a stoneware body (mid or high fire body).  Don't know what is meant by  using "normal glazes".  The glaze has to fit the clay---essentially means meant for the same cone.  You wouldn't expect great results from putting a ^04 glaze on a ^6 body and firing it to ^6, or putting a ^5 glaze on a ^05 body.   I single fire (^5) almost all the time and with my programmable kiln usually just do a slow glaze/slow cool program.  As a planter, it needs to be vitrified or it may crack --here's a link to some basic info.   http://cubits.org/mudders/articles/view/449/

 

Edited by LeeU
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@jacqui sos I'm still experimenting and only single fired twice, each time along with other bisqued pieces. 

Use the same firing schedule you normally use for the clay you have and use the same glaze as if you where firing bisqued pots.

Also, it seems the glazes needs to be applied thicker when single firing.

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