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Help! I Forgot To Bisque Before Glazing.


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So, I've been working on two slab projects for the last 2 weeks. Both of them have some pieces in the 3rd dimension as well as lots of 2D detail. I finished constructing both pieces today and despite how shaky my hands were, managed to paint both almost immaculately. Thing is, I forgot to give them a bisque firing before I jumped into glazing them. They're so detailed that there's no way I can remove the glaze without destroying the work in the process, so unless there's another way to make finished work out of them, they're garbage and I wasted my time, materials, and effort.

 

My instructor must have felt really bad for me, because as I was sticking the pieces back on the rack and deciding whether or not to trash them she came over and decided my stuff was special enough that we were going to try a risky operation, putting both pieces through both bisque firing and final firing despite them being glazed out of order. She says that the color won't be as consistent and you couldn't eat off of them (fine by me, because they're not dishes), but they should still stick together and come out okay.

 

Before we try this, however, I wanted to take some initiative and research both the risks of this test and any alternatives. Despite my excellent googling skills, I haven't been able to find an article or forum topic specific enough to my situation, so I figured I'd start one myself. Any and all information you can give me will be useful. I just want to know what might happen if we try to fire this thing and/or if there are any other ways to save the work with less risk involved.

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There are lots of glazes that can withstand being applied to greenware, then go through a bisque firing and a glaze firing. And there are some that won't make it. The fit just won't match and the glaze will flake off during the bisque. I once did this with my students on purpose. The ones that worked the best had a thin application of glaze. The thicker the glaze, the more likely it was to flake off during the bisque fire. 

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what do you worry about most?  single firing is not that unusual.  i fire that way all the time but i do uniform thickness to my  work and know what to expect when i do it.  firing pieces that are raw and pieces that are bisqued and refiring finished glazed pieces at the same time does not cause problems either.   the speed at which you go up to about 1200 degrees probably means more than anything else.  i know the temp where most people consider conversion is about 900 but i am talking about an entire kiln load steaming away the water vapor.  it takes time and 1200 is my safety number.

Edited by oldlady
clarity
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If this is a classroom situation, the glaze firing is probably not programmed to go up to bisque temp slowly enough for a green pot. It does not make sense for them to program a kiln for a once-firing that only contains two pieces. OP should put the pieces into a bisque firing first, then a glaze firing.

 

If the glazes flake off or do anything weird in the bisque firing, you can touch up your pieces with glaze before they go in the glaze firing.

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  • 4 years later...
  • 1 year later...
1 hour ago, aliceb said:

@neilestrick  Commercial clear glaze that can be applied to greenware or wet clay is preferred. I greatly appreciate any guidance from you. 

There's no definitive answer, because every clay body and glaze is different, but many many commercial glazes will work just fine when applied to greenware. Ultimately you'll just have to test one, but chances are you'll have good luck. I would test it on something you don't ca re about first, just in case. Applying to bone dry would be easiest, since it's porous. Leather hard could work, too, but it'll take a lot longer to dry between coats.

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Only thing I can add to all these which has been indirectly mentioned, Once fire goods will follow a much slower schedule than normal glaze firings. So to me a glaze firing is typically 7-9 hours and, Bisque is let’s say 9 - 12 hours.  Lots of folks who once fire just do a cone 6 automatic bisque instead of a cone six automatic glaze in the land of automatic controllers. All that off gassing needs time to make its way out of the wares and through the glaze coating. So the suggestion would be to use a bisque type schedule but fire to your final glaze cone. Some glazes will work better than others in once fire. Testing of the body and glaze is likely the only answer.

Edited by Bill Kielb
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alice, do you plan to dry out the pieces before firing?  are you saying "wet clay" because it is still damp?    should your question read "can i single fire these pieces using the glaze i currently use? "   then name the clay and the glaze i assume you already have.   i single fire all the time and have had no problems using the clay and the glazes that other people bisque fire before glazing.  be sure to include the cone number of the mature clay and glaze.  

the more you clarify what and why you are doing this, the better answers you will get.  bill gives you a lot to go on but you have not said you have a kiln at all, let alone one with an electronic controller.

 

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@oldlady     Thank you so much, I plan on drying them to bone dry before applying the clear glaze.  I have a manual kiln and I will be using a low fire clay body.  

I bought the Mayco S-2101 Crystal Clear Brushing glaze, but on the bottle reads to apply to bisque, and not greenware. 

 

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@neilestrick @oldlady  Thank you so much, I appreciate all of your guidance. I plan on drying them to bone dry before applying the clear glaze.  I have a manual kiln and I will be using a low fire clay body.  

I bought the Mayco S-2101 Crystal Clear Brushing glaze, but on the bottle reads to apply to bisque, and not greenware. 

 

 
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@oldlady   @neilestrick  

Thank you so much, your assistance is greatly appreciated!

Can I single fire pieces using Mayco S-2101 Crystal Clear Brushing glaze? Dickblicks site reads yes, but on the bottle it reads to apply to bisque, and not greenware. I reads to apply to cone 04 bisque. Then dry thoroughly and fire to shelf cone 06.

I am using a low fire clay body, (cream white earthenware) the cone number of the mature clay is 06-04. I am using a Manual Kiln with sitter. 

I plan on letting the pieces dry to bone dry before applying the clear glaze.

Does anyone know which brand makes a clear glaze that can be applied to either bone dry, greenware or wet clay? 

Thank you very much !

Edited by aliceb
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i don't think it is a question of if it can be used on greenware, i believe you would have a hard time brushing any glaze on greenware that has any texture without ruining the texture.    all of this is just my opinion, i spray my glazes so i do not have that problem.   i have sprayed commercial glazes as well as ones i mixed using readily available recipes.

remember, the manufacturers have to deal with people who have absolutely no knowledge and think glaze is like paint and greenware must be just like plaster so they do really stupid things.   the manufacturer is trying to cover as many possibilities to prevent problems.   it is safer for them to recommend bisquing first.   just think about a total novice wetting the piece so much that it collapses, brushing the nose off a figurine, any other insane thing someone can imagine.

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