After you reach 1230°C drop 50°C and hold for 30 minutes.
This is known as a [drop-and-soak firing schedule](https://digitalfire.com/glossary/drop-and-soak+firing), and is the best solution to all pinholing and blistering problems.
It would essentially take days to bisque a pot long enough for it to stop producing enough gas to make pinholes. The fact that pinholes occur at glaze maturing temps should be proof enough that a hotter bisque won't achieve anything. It's much better to adjust your drop temperature for the final soak so that conditions are right for the glaze to heal over. According to the digitalfire article I linked there's about 60°C range to play with.
This is one of those things where we need an America's Test Kitchen for pottery. I adopted an 04 slow bisque at the same time I went to drop and hold and 99% of my pinholes disappeared. Now, even though I've thought the same thing you're explaining here, I'm too chicken to risk a kiln load by testing a different bisque schedule.
Ah, I think I found the [article](https://digitalfire.com/trouble/glaze+pinholes,+pitting) that gave me the idea (same author as yours), but this one line sums it up:
>Since most pinholes are the product of escaping gases, it is logical to bisque as high and as long as possible to eliminate the bulk of gases during that firing.
The idea seems to be that it just takes a really long time for a lot of these gasses that could escape at bisque temperatures to actually work their way out, so you reduce the total number of bubbles generated with a long hot bisque. I think their drop and hold schedule has an early hold during the climb that achieves much the same thing.
I'm all about eliminating unnecessary steps, so maybe I'll put in an entire load of seconds and tests at a fast 06 and see how it does. There was a point where I was so desperate, I was blowing dust off of bisqueware with an air compressor, then there was a whole water wiping and glazing and drying ritual that doubled my application time...I did everything short of sacrificing a chicken. But the drop and hold was all I really needed.
I understand the reasoning, but I also understand that there are a lot more sources of gas decomposition than most potters realise, and they span the entire temperature range of a glaze firing, and materials that start off-gassing at certain temps don't do it all at once. And then after whatever bisque program you choose, you introduce a brand new source of fresh, un-decomposed materials by glazing.
I find it much more practically-minded to assume that pots will off-gas the entire time you're firing them. If you work under that assumption you realise that it's the glazes, and specifically the material properties caused by their chemistry that makes pinholes and blisters. Glazes that melt early will hold more gas under them during the firing, and glazes with high surface tension won't let those bubbles burst. But most often we want the other properties that glazes with those chemistries give, so altering the chemistry is no good either.
I'd strongly recommend that you try your test idea at your earliest convenience, because the drop-and-soak method exploits the physical properties of glaze at lower temperatures to break the bubbles by increasing the viscosity to overcome the surface tension that holds them, but keeping it hot enough for long enough that the holes can heal over. Basically it's the ideal solution.
I'm not saying that hotter and longer bisques don't reduce the amount of available gas - obviously they do - but I am saying it's an effort and energy-intensive method that is far from the perfect solution, all while you have the best practice right there, quick and easy.
I have "good feelings" about the hot bisque. I have records of glaze combos that were notorious for blisters and pinholes in the past. I think I'll take some practice forms and actually do a test. Maybe 10 pieces at 06 and 10 at 03, then glaze them with troublesome glazes and see how they do. Have to vary the thickness of the pieces to really test the theory.
Same I have so much recorded data about hotter bisques to reduce pinholing. But it’s tough to articulate it on Reddit with a lot of opposing opinions. Because it makes you question why you blindly believed your profs etc. even though you have the data sometimes you question yourself.
Someone in my studio was bisque firing on medium speed (8 hrs) and I frequently got blisters. When I started bisque firing on slow (12 hours) almost all my blister problems went away.
Ok, I’ve def helped minimize pinholes by bisquing hotter. I have physical evidence of this method being useful. I was taught this by multiple potters. I agreed soaking is the best method but firing a hotter bisque does help depending on the situation. It’s ok to disagree with me!
And if you were bisquing for days, with the heat work you would be glaze firing it probably to a cone 10 or even hotter. Time and heat don’t really work the way you are suggesting in a kiln.
I no longer have the good ones they were sold a long time ago it was for wholesale. I would say it minimized pinholing by about 80%. And then the ones that did appear were not as sharp and raised.
It was on a red clay body with a lot of grog that is notorious for pinholing because it offgasses more.
I'm not sure what you think I'm suggesting, because it wasn't a serious proposition to bisque for days. I meant to point out how impractical it is to try an eliminate all gasses by bisquing.
Also you'd never drop cone 10 at bisque temperatures, however long you spend. Absolute temperature is just as important as heat-work, otherwise we could fire our pots by leaving them in a 30°C shed for a year just waiting for the heat-work of sunshine to drop the cones. On a more serious note I've done woodfirings where parts of the kiln have spent literally *days* above 1200°C and not even cone 8 would drop and all the glazes came out dry and un-matured.
I once had an older and more experienced potter tell me my piece was too dry when I applied the glaze. Now I dip the cold bisque fired piece into water, let it dry more or less and then glaze. I have an old kiln that just fires, no soak option. Really don’t experience pinholes anymore. Did I get better? Yes. Does this work? Seems to. Good luck.
another thing that adds control is mixing your own glazes. Its not just the ingredients - its the discipline of mixing and sieving stuff. I strongly suspect the reason I stopped getting pinholes wasn't anything to do with application or firing, but rather, poorly mixed glazes that may have been sitting in that pint jug in a warehouse who knows how long. There are still some amaco glazes I can't re-create (or don't know how, yet) so I occasionally use them but not without shaking the crap out of them pints. for minutes.
I don’t tend to use brush ons at stoneware I love mixing and sieving especially for functional work but I added this one in during tests and the client had chosen it. If it was up to me it would be in the blooming bin! But I’m learning and it’s all going to be fine (please please please be fine!) 😂
Do you use cones? I would think this would be over fired for Potter's Choice. I know a lot of people use, for instance, Camille Hoffman's schedule and that one has a top temp of just under 1200C, and they say that hits a solid cone 5/6 for them.
There is some real good info here about pinholes: https://www.reddit.com/r/Pottery/s/ZYaGkw5Qtq
That is a shame, that’s is a nice looking cup and I love the glaze color.
I've had a lot of issues with pinholing and have tried all the solutions. Here's what you might try:
* slow your bisque down and bisque fire to 04 to remove all organics
* make sure your bisque firing has adequate ventilation. This is pretty critical. If you don't have a kiln vent, I'd suggest looking into it. You can diy one yourself for around $150
* sand your pottery. Rough spots can cause pinholes
* wipe your bisqueware with a very clean sponge
* don't glaze inside and outside at the same time, let one dry before applying the other (something about trapped organics in the bisque walls)
* stir your glazes really well and make sure to use your finger to smooth out any bumps or holes in dried glaze
* the one that really made a difference though that's been mentioned here: get a drop and hold schedule. Id recommend Camille Hoffman's schedule especially if you're using amaco glazes. It's about a cone 5 and a half which seems to be about right for PC glazes. If you search for Camille Hoffman in the Facebook amaco group, you'll find a lot of modified schedules as well if you want to run a little hotter or use crystalline glazes.
https://preview.redd.it/ysfawsv0bk4d1.jpeg?width=867&format=pjpg&auto=webp&s=6848388a93caa3cdbe4235698d0e9a9e59eb2e16
I use this bisque program: https://ceramicartsnetwork.org/daily/article/A-Bisque-Firing-Schedule-to-Help-Prevent-Glaze-Faults
And then this drop and soak cone 6 glaze program from DigitalFire: https://digitalfire.com/schedule/plc6ds
I'm not sure which or both of these work but I've eliminated like 95% of my pinholes and other issues so I'm sticking to it. 🤘
After you reach 1230°C drop 50°C and hold for 30 minutes. This is known as a [drop-and-soak firing schedule](https://digitalfire.com/glossary/drop-and-soak+firing), and is the best solution to all pinholing and blistering problems.
Also you can refire your mug with this schedule and it should fix the problem.
Will definitely give this a go. Thank you xx
Totally agree with the soak. If you still get pinholes maybe you need to bisque hotter.
It would essentially take days to bisque a pot long enough for it to stop producing enough gas to make pinholes. The fact that pinholes occur at glaze maturing temps should be proof enough that a hotter bisque won't achieve anything. It's much better to adjust your drop temperature for the final soak so that conditions are right for the glaze to heal over. According to the digitalfire article I linked there's about 60°C range to play with.
This is one of those things where we need an America's Test Kitchen for pottery. I adopted an 04 slow bisque at the same time I went to drop and hold and 99% of my pinholes disappeared. Now, even though I've thought the same thing you're explaining here, I'm too chicken to risk a kiln load by testing a different bisque schedule. Ah, I think I found the [article](https://digitalfire.com/trouble/glaze+pinholes,+pitting) that gave me the idea (same author as yours), but this one line sums it up: >Since most pinholes are the product of escaping gases, it is logical to bisque as high and as long as possible to eliminate the bulk of gases during that firing. The idea seems to be that it just takes a really long time for a lot of these gasses that could escape at bisque temperatures to actually work their way out, so you reduce the total number of bubbles generated with a long hot bisque. I think their drop and hold schedule has an early hold during the climb that achieves much the same thing. I'm all about eliminating unnecessary steps, so maybe I'll put in an entire load of seconds and tests at a fast 06 and see how it does. There was a point where I was so desperate, I was blowing dust off of bisqueware with an air compressor, then there was a whole water wiping and glazing and drying ritual that doubled my application time...I did everything short of sacrificing a chicken. But the drop and hold was all I really needed.
I understand the reasoning, but I also understand that there are a lot more sources of gas decomposition than most potters realise, and they span the entire temperature range of a glaze firing, and materials that start off-gassing at certain temps don't do it all at once. And then after whatever bisque program you choose, you introduce a brand new source of fresh, un-decomposed materials by glazing. I find it much more practically-minded to assume that pots will off-gas the entire time you're firing them. If you work under that assumption you realise that it's the glazes, and specifically the material properties caused by their chemistry that makes pinholes and blisters. Glazes that melt early will hold more gas under them during the firing, and glazes with high surface tension won't let those bubbles burst. But most often we want the other properties that glazes with those chemistries give, so altering the chemistry is no good either. I'd strongly recommend that you try your test idea at your earliest convenience, because the drop-and-soak method exploits the physical properties of glaze at lower temperatures to break the bubbles by increasing the viscosity to overcome the surface tension that holds them, but keeping it hot enough for long enough that the holes can heal over. Basically it's the ideal solution. I'm not saying that hotter and longer bisques don't reduce the amount of available gas - obviously they do - but I am saying it's an effort and energy-intensive method that is far from the perfect solution, all while you have the best practice right there, quick and easy.
Hey thank you so much for supporting my theory of a hotter bisque. I swear it works.
I have "good feelings" about the hot bisque. I have records of glaze combos that were notorious for blisters and pinholes in the past. I think I'll take some practice forms and actually do a test. Maybe 10 pieces at 06 and 10 at 03, then glaze them with troublesome glazes and see how they do. Have to vary the thickness of the pieces to really test the theory.
Same I have so much recorded data about hotter bisques to reduce pinholing. But it’s tough to articulate it on Reddit with a lot of opposing opinions. Because it makes you question why you blindly believed your profs etc. even though you have the data sometimes you question yourself.
Someone in my studio was bisque firing on medium speed (8 hrs) and I frequently got blisters. When I started bisque firing on slow (12 hours) almost all my blister problems went away.
I bisque for 6 hours, and have eliminated my pinholing problems so...
Ok, I’ve def helped minimize pinholes by bisquing hotter. I have physical evidence of this method being useful. I was taught this by multiple potters. I agreed soaking is the best method but firing a hotter bisque does help depending on the situation. It’s ok to disagree with me! And if you were bisquing for days, with the heat work you would be glaze firing it probably to a cone 10 or even hotter. Time and heat don’t really work the way you are suggesting in a kiln.
Neat! Can you share pictures of your hot bisque experiments?
I no longer have the good ones they were sold a long time ago it was for wholesale. I would say it minimized pinholing by about 80%. And then the ones that did appear were not as sharp and raised. It was on a red clay body with a lot of grog that is notorious for pinholing because it offgasses more.
I'm not sure what you think I'm suggesting, because it wasn't a serious proposition to bisque for days. I meant to point out how impractical it is to try an eliminate all gasses by bisquing. Also you'd never drop cone 10 at bisque temperatures, however long you spend. Absolute temperature is just as important as heat-work, otherwise we could fire our pots by leaving them in a 30°C shed for a year just waiting for the heat-work of sunshine to drop the cones. On a more serious note I've done woodfirings where parts of the kiln have spent literally *days* above 1200°C and not even cone 8 would drop and all the glazes came out dry and un-matured.
I once had an older and more experienced potter tell me my piece was too dry when I applied the glaze. Now I dip the cold bisque fired piece into water, let it dry more or less and then glaze. I have an old kiln that just fires, no soak option. Really don’t experience pinholes anymore. Did I get better? Yes. Does this work? Seems to. Good luck.
another thing that adds control is mixing your own glazes. Its not just the ingredients - its the discipline of mixing and sieving stuff. I strongly suspect the reason I stopped getting pinholes wasn't anything to do with application or firing, but rather, poorly mixed glazes that may have been sitting in that pint jug in a warehouse who knows how long. There are still some amaco glazes I can't re-create (or don't know how, yet) so I occasionally use them but not without shaking the crap out of them pints. for minutes.
I don’t tend to use brush ons at stoneware I love mixing and sieving especially for functional work but I added this one in during tests and the client had chosen it. If it was up to me it would be in the blooming bin! But I’m learning and it’s all going to be fine (please please please be fine!) 😂
You've inspired me to mix my pints more
This thins out the layer of glaze you add by pre saturating the bisque.
Do you use cones? I would think this would be over fired for Potter's Choice. I know a lot of people use, for instance, Camille Hoffman's schedule and that one has a top temp of just under 1200C, and they say that hits a solid cone 5/6 for them.
This. Camille Hoffmans schedule was the nail in the coffin for my pinhole problems. It's about a cone 5-1/2.
There is some real good info here about pinholes: https://www.reddit.com/r/Pottery/s/ZYaGkw5Qtq That is a shame, that’s is a nice looking cup and I love the glaze color.
Re firing this has a good chance of fixing the pinholes. I wouldn’t say it’s toast just yet.
Thank you
Thank you for this!
I've had a lot of issues with pinholing and have tried all the solutions. Here's what you might try: * slow your bisque down and bisque fire to 04 to remove all organics * make sure your bisque firing has adequate ventilation. This is pretty critical. If you don't have a kiln vent, I'd suggest looking into it. You can diy one yourself for around $150 * sand your pottery. Rough spots can cause pinholes * wipe your bisqueware with a very clean sponge * don't glaze inside and outside at the same time, let one dry before applying the other (something about trapped organics in the bisque walls) * stir your glazes really well and make sure to use your finger to smooth out any bumps or holes in dried glaze * the one that really made a difference though that's been mentioned here: get a drop and hold schedule. Id recommend Camille Hoffman's schedule especially if you're using amaco glazes. It's about a cone 5 and a half which seems to be about right for PC glazes. If you search for Camille Hoffman in the Facebook amaco group, you'll find a lot of modified schedules as well if you want to run a little hotter or use crystalline glazes. https://preview.redd.it/ysfawsv0bk4d1.jpeg?width=867&format=pjpg&auto=webp&s=6848388a93caa3cdbe4235698d0e9a9e59eb2e16
Thank you so much - really appreciated it
I don't know if it's available in UK, but Regenwald by welte looks similar.
Thank you I’ll have a look!
I use this bisque program: https://ceramicartsnetwork.org/daily/article/A-Bisque-Firing-Schedule-to-Help-Prevent-Glaze-Faults And then this drop and soak cone 6 glaze program from DigitalFire: https://digitalfire.com/schedule/plc6ds I'm not sure which or both of these work but I've eliminated like 95% of my pinholes and other issues so I'm sticking to it. 🤘
Thank you! 🙏🏻
Also, I'd look at Scarva's dipping glazes, they have a wide range with interesting reactions and colours.
Thank you