The studio I work in had a misfiring, and I glazed some pieces I thought had been bisqued, but were actually still greenware. They haven't been fired yet, but I am wondering if I can just high-fire them as if they had been bisqued. I've heard that there is a way to skip the bisque step, but I wasn't sure of the details and don't want to mess anything up. Can someone tell me what I should do with these pieces?
Thanks, Mandy
Mandy: Unless you planned to fire those pieces to a cone less than bisque (^04-^06), or the glaze used is good only for lower temps than that, then why would you want to skip the bisque firing just because they are now glazed?
You can still fire them bisque first, then touch up the glaze and refire.
If you are planning on doing a single firing, I would fire very slowly (especially early temp increases), and let the pieces soak at about 200C and again at 600C for a few hours or more (each temp) to burn off any moisture, and help with the quartz inversion, then proceed normally from 600C to whatever cone.
You will probably (likely) get some unexpected results with the glaze from the reaction with the clay body, though, since the body is still greenware, and subject to absorption/transfer issues between it and the glaze. Glaze fit may also be an issue, depeding on your shrinkage rates for each, clay and glaze.
You might want to clean off (most of) the glaze with a white scrubbing pad (like a green pad, but not abrasive), then send the pieces through a bisque firing. If the pieces are heavily decorated with different glazes, it's a lot of time spent for naught; but safer and more predictable results will happen if you clean off and start over. You can chalk it up to experience, and not time wasted, if that helps. Good Luck! Wayne Seidl
Would it not be easier to take the glaze off after the bisque?
I would put one piece through a bisque, then a glaze firing and see how it comes out. When I was first experimenting with raw glazing I found that several of my glazes worked very well provided I applied them to bone dry wares. I raw glaze as a matter of course these days and when I'm firing in someone else's kiln I bisque the pieces to ensure they travel well!
Steve Bath UK
In article , Mandy Farrier writes
Hi Mandy,
Wow!, Disneyland and ceramics, what wonderful inspiration you will have to create!
The glaze, if left on as it is now, will fuse to the clay and will be impossible to remove after bringing the clay to bisque temperature.
I think what Wayne was trying to say is you could leave the pieces as they are now, with glaze on them, take the pieces to bisque then reglaze if necessary, but do it slowly as moisture might be trapped in the clay because of the "green" glazing. Then, after reglazing, take the pieces up to the designated cone the clay and glaze were formulated for.
Please correct me, Wayne, if I'm misguided :)
Diego
No Diego, right on target...you put it quite eloquently, and with far fewer words than I did. Nice job! Best Regards, Wayne Seidl
The studio I work in low fires students work with a clear glaze on it all the time. Sometimes they will use colored slips prior to the clear low fire glaze....it works. Marlynn
It depends on the fit of the glaze to the clay... how forgiving or what range you have on the glaze. Recently a woman in our pottery studio took a bisque piece that had cracked, glazed it, put thin pieces of still workable (wet) clay over the cracks as patches. She then put glaze on these "greenware" patches and fired it. It came out beautifully. Do a test of a small piece and see what you think. I would however have the test piece internal to some other piece that you don't much care about.
DKat
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