cdudley Posted April 23, 2020 Report Share Posted April 23, 2020 Hi clay friends I know it isn't advisable. But I have limited time and access, and a bunch of porcelain. I hand build with slabs to make hanging wall pieces, think large "platters" or concave mirror like shapes. I'm going to try a pit fire in my yard in the next two weeks (I have a show June 1 and haven't been able to fire due to COVID for over a month). I've read as much as I can find on the internet, and am still having trouble getting good advice on pit firing porcelain. I've got my hands on all the combustible colorants, terra sig, etc., but I'm most concerned about the pieces shattering. I've seen mention of pre-heating, but what does that entail? Does it defeat the purpose if the piece cools down between the preheat and the big fire (I will only be able to fit one or two in my grill for preheating at a time)? And should I try to keep the main fire low? Again I know its not the best situation but I think, especially in this time we are living in, its interesting to make due with what I have on hand and see what can come out of it. And I'm prepared for a lot of loss. Any advice would be helpful! Thank you. Link to comment Share on other sites More sharing options...
Babs Posted April 23, 2020 Report Share Posted April 23, 2020 Have they been bisqued? Link to comment Share on other sites More sharing options...
liambesaw Posted April 23, 2020 Report Share Posted April 23, 2020 57 minutes ago, Babs said: Have they been bisqued? Very important question, because if not, I don't see much use in pit firing! If you're looking for a way to fire these yourself from greenware stage to vitrification, you will want to build a makeshift kiln out of clay instead of trying to fire it in a pit fire. Pit fire would have a really hard time reaching temperatures required to convert clay to ceramic. But enclose the fire and allow some kind of draft to flow through, and you can easily reach bisque temperatures. There are many primitive kilns on YouTube, it's mostly an elevated pit with a chimney made of clay, you stack the objects in the chimney, and then keep the fire in the pit underneath filled with wood (or charcoal or whatever) so that the flames and air are able to move through the work. Just putting stuff in a pit will only get to temperatures that a campfire would get to, which is not really hot enough. Link to comment Share on other sites More sharing options...
cdudley Posted April 23, 2020 Author Report Share Posted April 23, 2020 1 hour ago, Babs said: Have they been bisqued? Unfortunately, no they have not. Link to comment Share on other sites More sharing options...
cdudley Posted April 23, 2020 Author Report Share Posted April 23, 2020 8 minutes ago, liambesaw said: If you're looking for a way to fire these yourself from greenware stage to vitrification, you will want to build a makeshift kiln out of clay instead of trying to fire it in a pit fire. I'm not expecting them to get to vitrification, but don't people pit fire with high fire clay and get interesting results? I understand it wont be the most durable. However I will look into the primitive kilns, thank you. Link to comment Share on other sites More sharing options...
liambesaw Posted April 23, 2020 Report Share Posted April 23, 2020 5 minutes ago, cdudley said: I'm not expecting them to get to vitrification, but don't people pit fire with high fire clay and get interesting results? I understand it wont be the most durable. However I will look into the primitive kilns, thank you. They pit fire bisqued pieces for interesting results. The idea is that you bisque fire so that the clay body is still "open" and will take carbons and other colorants, but strong enough to be handled, and won't turn back to mud. Link to comment Share on other sites More sharing options...
cdudley Posted April 23, 2020 Author Report Share Posted April 23, 2020 20 minutes ago, liambesaw said: They pit fire bisqued pieces for interesting results. The idea is that you bisque fire so that the clay body is still "open" and will take carbons and other colorants, but strong enough to be handled, and won't turn back to mud. so do you think the colorants would burn off before the greenware clay body became porous enough to accept them? Link to comment Share on other sites More sharing options...
liambesaw Posted April 23, 2020 Report Share Posted April 23, 2020 7 minutes ago, cdudley said: so do you think the colorants would burn off before the greenware clay body became porous enough to accept them? No, the clay will be porous enough to accept them, I just think it would be difficult to become ceramic in a pit fire. SO it may look beautiful, but at the same time it could still be slaked down back to clay. The idea of bisquing it first, is that it will cross that chemical water threshold, and will never become clay again, and it will be strong enough to withstand the rapid firing, while still being able to take color. Link to comment Share on other sites More sharing options...
cdudley Posted April 23, 2020 Author Report Share Posted April 23, 2020 What if I fired the work wrapped in foil (in a pit, or primitive kiln, or large smoker bbq, TBD) to as close as I can estimate to cone 010, then let them cool, then fired them in the pit with the colorants? Link to comment Share on other sites More sharing options...
liambesaw Posted April 23, 2020 Report Share Posted April 23, 2020 I say give it a try! Link to comment Share on other sites More sharing options...
cdudley Posted April 23, 2020 Author Report Share Posted April 23, 2020 9 minutes ago, liambesaw said: No, the clay will be porous enough to accept them, I just think it would be difficult to become ceramic in a pit fire. SO it may look beautiful, but at the same time it could still be slaked down back to clay. The idea of bisquing it first, is that it will cross that chemical water threshold, and will never become clay again, and it will be strong enough to withstand the rapid firing, while still being able to take color. ok, I think I'm getting it -- so do you think that the bisque fire is hotter/longer than the pit fire and that's why its necessary for the work to become ceramic? Link to comment Share on other sites More sharing options...
liambesaw Posted April 24, 2020 Report Share Posted April 24, 2020 47 minutes ago, cdudley said: ok, I think I'm getting it -- so do you think that the bisque fire is hotter/longer than the pit fire and that's why its necessary for the work to become ceramic? Yep! Youre basically removing that sintering step from the equation when you bisque first. Link to comment Share on other sites More sharing options...
Babs Posted April 24, 2020 Report Share Posted April 24, 2020 I think it can also reduce risks of fatal temp changes and allows for controlled slow rise. Many primitive potters successfully pit fire but they know their clay and their fuel... Their choice would not be porcelain.. Some great sources around... Perhaps pm Marcia Selsor. She has built amazing quick kilns Link to comment Share on other sites More sharing options...
Sorcery Posted April 26, 2020 Report Share Posted April 26, 2020 I say go for it too. But if you can pitfire....you can woodfire! Sorce Link to comment Share on other sites More sharing options...
neilestrick Posted April 26, 2020 Report Share Posted April 26, 2020 1 hour ago, Sorcery said: I say go for it too. But if you can pitfire....you can woodfire! Sorce How so? They're completely different processes and kilns... Link to comment Share on other sites More sharing options...
neilestrick Posted April 26, 2020 Report Share Posted April 26, 2020 Porcelain is not usually the best candidate for things like pit firing and raku and such because it doesn't deal with thermal shock very well. However I think it's worth trying. One of the problems with not bisque firing before pit firing is that the pots tend to blow up from heating too quickly. But porcelain has a much lower clay content than most clay bodies, so it dries faster and gives up moisture faster, so it may actually be less likely to blow up from the rapid heating of a pit firing. That said, the uneven heating may still be a problem. Give it a try, though. It may be amazing! Link to comment Share on other sites More sharing options...
Sorcery Posted April 26, 2020 Report Share Posted April 26, 2020 4 hours ago, neilestrick said: How so? They're completely different processes and kilns... As far as ordinances go, or what one can get away with. Sorce Link to comment Share on other sites More sharing options...
neilestrick Posted April 26, 2020 Report Share Posted April 26, 2020 6 hours ago, Sorcery said: As far as ordinances go, or what one can get away with. Sorce I see what you're saying. But if you're building a wood kiln that's anything beyond a very small primitive model that no one will really notice, there may be ordinances at play beyond just whether or not open burning is allowed. Link to comment Share on other sites More sharing options...
Sorcery Posted April 26, 2020 Report Share Posted April 26, 2020 3 hours ago, neilestrick said: I see what you're saying. But if you're building a wood kiln that's anything beyond a very small primitive model that no one will really notice, there may be ordinances at play beyond just whether or not open burning is allowed. With caution thrown directly into the wind, so it comes right back, and keeps us safety conscious.... I hope this Corona makes everyone build a wood kiln! No one's looking! Lol. Hey, I think I found out today why these electric kilns aren't supported by the case. The screws, that inevitably go into the brick, can't take the shear force they face, if pressure is put up on the SS only. I'm 157F into the second firing of this gas joint. Little nervous but so far so good! Sorce Link to comment Share on other sites More sharing options...
cdudley Posted April 27, 2020 Author Report Share Posted April 27, 2020 thanks everyone for your advice so far! I did some 'digging' (heh) in my community and found somewhere I can drop off for bisque firing! So that should improve my success rate a bit, but I'll still be working with porcelain . My plan is two thin layers of terra sigillata, bisque to cone 010, then pit firing with the colorants- oxides, metal wires, organic materials. So if I bisque I won't need to preheat, correct? I have some test tiles that are small versions of my larger pieces so I'll do a test fire, but as I said they are sort of like very shallow platters and I'm thinking about positioning in the pit; would be safest for them to lie flat but would it be better for the colorants and flashing for me to fashion some way to fire them vertically? Everything I've found online for pit firing is pots, so they easily sit upright, and I'm wondering if the work needs to be upright to accept colors, because of air flow or the way the combustibles will move or something like that. And any other advice for a first timer? Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted April 27, 2020 Report Share Posted April 27, 2020 56 minutes ago, cdudley said: And any other advice for a first timer? Yep, always stand up wind! LT Link to comment Share on other sites More sharing options...
Babs Posted April 27, 2020 Report Share Posted April 27, 2020 Still go gently. Thermal shock by quick increase and sudden drops draughts and flare up situations will be your worst enemy. Stacking is important because depending on your stack you may have pots drop and shift with fuel turning to ash . Having a biggish pot central in pit ..even a prefired one and stack lean your platers around it may be best for airflow and avoiding densely packed platters. Can't wait to see results! Some one in these forums did a pit firing and wrote about it .... Bisquing will give you a better chance Link to comment Share on other sites More sharing options...
cdudley Posted May 5, 2020 Author Report Share Posted May 5, 2020 Hi Friends! I'm so excited to share the results from my first round! I did a small test fire and was happy with the results so I went for it with these bigger ones. For scale, the table they are on is 4 ft wide and I haven't polished them yet. I did have one piece crack into three separate chunks but I figure 75% success rate is pretty good for a newb! I have 6 more to go. Two of these have teeny hairline cracks that I'm going to try and heal by covering the back with epoxy, as long as it doesn't crack any more, the piece can still hang on the wall and function as intended. I ended up just laying them flat on the bottom of the pit, no stacking. Thanks for everyones help. Now having experienced the process, I'm sure that bisque firing first was pretty much necessary. Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted May 5, 2020 Report Share Posted May 5, 2020 40 minutes ago, cdudley said: I did have one piece crack into three separate chunks but I figure 75% success rate is pretty good for a newb! Well done! not too far back in time a student colleague had a platter carved with a mimbres design that cracked into several large pieces during the firing about two days before her critique. I suggested that she attach the three pieces to a thin piece of stiff cardboard or the backing of a picture frame. that she got a frame and mounted the pieces; the prof and her classmates commented that the cracks and the frame made the artwork more interesting. so: Take the "shards" and assemble them on a backing and see what happens visually. LT Link to comment Share on other sites More sharing options...
Min Posted May 5, 2020 Report Share Posted May 5, 2020 You got some nice colour there, they look great! Link to comment Share on other sites More sharing options...
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