Ryleigh Posted June 11, 2020 Report Share Posted June 11, 2020 Hello! I am in a bit of a predicament at the moment… My kiln is currently down because I’m waiting on a new thermocouple.. I have a business partner that needs a prototype ornament by Monday of next week (4 days). I am making the ornament out of white sculpture earthenware clay that fires to cone 06-04, the commercial glaze I have fires to 05. When talking to a friend he said to go ahead and glaze it once it was bone dry and single fire it. So, I went ahead and glazed my ornament after it was bone dry. I called the place that I get my supplies from to make sure I was firing my test kiln correctly, and he informed me that doing a single fire with the white earthenware was not something I should be doing... Is single fire okay for this ornament or should I scrap it? I know single fire isn’t uncommon, but I have never done it before. The test kiln is a Vulcan JK-1. I know these kilns fire much faster and cool down much faster than large kilns, so I am unsure how to fire it properly if I have a single fire piece in it.. Since my piece is single fire it needs a longer fire time, correct? How long should I fire for to get the best results? Link to comment Share on other sites More sharing options...
Bill Kielb Posted June 11, 2020 Report Share Posted June 11, 2020 25 minutes ago, Ryleigh said: Hello! I am in a bit of a predicament at the moment… My kiln is currently down because I’m waiting on a new thermocouple.. I have a business partner that needs a prototype ornament by Monday of next week (4 days). I am making the ornament out of white sculpture earthenware clay that fires to cone 06-04, the commercial glaze I have fires to 05. When talking to a friend he said to go ahead and glaze it once it was bone dry and single fire it. So, I went ahead and glazed my ornament after it was bone dry. I called the place that I get my supplies from to make sure I was firing my test kiln correctly, and he informed me that doing a single fire with the white earthenware was not something I should be doing... Is single fire okay for this ornament or should I scrap it? I know single fire isn’t uncommon, but I have never done it before. The test kiln is a Vulcan JK-1. I know these kilns fire much faster and cool down much faster than large kilns, so I am unsure how to fire it properly if I have a single fire piece in it.. Since my piece is single fire it needs a longer fire time, correct? How long should I fire for to get the best results? Without testing it’s hard to know if the clay and glaze will work without some defects. What is important is you will be doing a slow bisque fire during this period, not a fast glaze fire so all the off gassing can occur. So you are correct, if I were trying this first time I would probably start with a cone fire automatic bisque to 05. This is likely Approximately a 12 hour schedule. If you have the automatic model then a search of your instruction book for slow bisque seems in order. Of course single fire folks usually test and come up with dependable combinations, so testing is always key. In this case I understand you are already committed. Link to comment Share on other sites More sharing options...
Ryleigh Posted June 11, 2020 Author Report Share Posted June 11, 2020 6 minutes ago, Bill Kielb said: Without testing it’s hard to know if the clay and glaze will work without some defects. What is important is you will be doing a slow bisque fire during this period, not a fast glaze fire so all the off gassing can occur. So you are correct, if I were trying this first time I would probably start with a cone fire automatic bisque to 05. This is likely Approximately a 12 hour schedule. If you have the automatic model then a search of your instruction book for slow bisque seems in order. My test kiln is completely manual, which is new to me. My full size kiln is automatic. Link to comment Share on other sites More sharing options...
neilestrick Posted June 11, 2020 Report Share Posted June 11, 2020 29 minutes ago, Ryleigh said: My test kiln is completely manual, which is new to me. My full size kiln is automatic. Low fire white bodies often do just fine when single firing with brush-on glazes. Just go slow. The bigger problem will be that your little test kiln is going to cool very quickly compared to a larger kiln, and that may affect the accuracy of the firing. You could fire it, and right when it shuts off, restart it by lifting the sitter weight, pressing the start button, and gently lowering the weight so it doesn't kick out the start button. Then put it on medium for an hour and half, then low for an hour and a half, then shut it off. It's not a perfect approximation of the cooling of a larger kiln, but it should get somewhat close. Ultimately it depends on if the prototype needs to be more accurate in size and shape, or in color. Of course, if you've used the glaze before, then you'll know if the color is right or not. Link to comment Share on other sites More sharing options...
Ryleigh Posted June 11, 2020 Author Report Share Posted June 11, 2020 38 minutes ago, neilestrick said: Low fire white bodies often do just fine when single firing with brush-on glazes. Just go slow. The bigger problem will be that your little test kiln is going to cool very quickly compared to a larger kiln, and that may affect the accuracy of the firing. You could fire it, and right when it shuts off, restart it by lifting the sitter weight, pressing the start button, and gently lowering the weight so it doesn't kick out the start button. Then put it on medium for an hour and half, then low for an hour and a half, then shut it off. It's not a perfect approximation of the cooling of a larger kiln, but it should get somewhat close. Ultimately it depends on if the prototype needs to be more accurate in size and shape, or in color. Of course, if you've used the glaze before, then you'll know if the color is right or not. Neil, thank you! For the cool down I was thinking something similar to what you said. For now I’m worried about the size and shape, the colors aren’t as much of a concern at the moment because she may want to change them anyway. For the initial firing I know it should be slow so that the glaze matures properly. I started the firing around 8am and it is already up to 500°... I have been turning it off and on periodically so it does not heat up too fast. Would 108° per hour till it reaches cone 05 be sufficient? At a rate of 108° per hour it would be 1886° for a final temp. Link to comment Share on other sites More sharing options...
neilestrick Posted June 11, 2020 Report Share Posted June 11, 2020 Don't worry too much about speed at the low end. If the piece hasn't blown up yet, it won't. Go slow from 850-1050, and go slow for the last 200 degrees, but don't overthink it. The worst that will happen is the glaze will be funky. Link to comment Share on other sites More sharing options...
Ryleigh Posted June 11, 2020 Author Report Share Posted June 11, 2020 2 minutes ago, neilestrick said: Don't worry too much about speed at the low end. If the piece hasn't blown up yet, it won't. Go slow from 850-1050, and go slow for the last 200 degrees, but don't overthink it. The worst that will happen is the glaze will be funky. I’m just now getting to 800. So after 1050° I should be okay to go a little faster till that last 200°? Since quartz inversion took place already, correct? That is true. Can’t do change anything now! Link to comment Share on other sites More sharing options...
neilestrick Posted June 11, 2020 Report Share Posted June 11, 2020 2 minutes ago, Ryleigh said: I’m just now getting to 800. So after 1050° I should be okay to go a little faster till that last 200°? Since quartz inversion took place already, correct? That is true. Can’t do change anything now! Yep. And we want to get all the organics burned out and not trapped in the glaze. Link to comment Share on other sites More sharing options...
Ryleigh Posted June 11, 2020 Author Report Share Posted June 11, 2020 5 minutes ago, neilestrick said: Yep. And we want to get all the organics burned out and not trapped in the glaze. Right! Thank you! Link to comment Share on other sites More sharing options...
Ryleigh Posted June 12, 2020 Author Report Share Posted June 12, 2020 On 6/11/2020 at 1:07 PM, neilestrick said: Yep. And we want to get all the organics burned out and not trapped in the glaze. It turned out better than expected. Definitely not perfect by any means, but it will do for now! There are lots of bubbles on the sides/edges of it. Thanks again. If I was going to fire my glazed stoneware (cone 6) would I do a similar firing? Slow down around 850-1050, then maybe medium rate before and after? Link to comment Share on other sites More sharing options...
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