Moh92 Posted October 24, 2021 Report Share Posted October 24, 2021 Hey everybody, I'm so glad to join this community . I'm a beginner and I've been doing pottery for 6 months now. I have few questions and I'd love to have some answers. I'm planning to make decorative objects/sculptures mostly not functional just as home décor ornaments and not more than 1 inch in thickness. I used many kinds of stoneware clay before but this time I wanna try PSH white porcelain #909 and black clay 540i and both are cone 6. The reason why I wanna try porcelain is that I want the fired piece to be an actual white and not warm yellowish white that white stoneware clay usually shows after firing. Just wondering if anyone has tried these 2 to make sculptures or ornaments or even vases/pots before, I'd like to know what are the cons and pros. Another question : is it neccessary to fire the pieces twice ?? I'm not planning on glazing them and wanna leave them with the raw finish black and white and only speckle some stuff on them with underglaze. Is there any cons for firing only once ? Thank you and sorry for the long topic Link to comment Share on other sites More sharing options...
Hulk Posted October 25, 2021 Report Share Posted October 25, 2021 Hi Moh! I haven't yet (and may never get around to it) tried working with porcelain, but have been through a bag of black (cone 5) clay. The black clay I tried fired to a very nice colour, smooth finish, and strong; it took several of my glazes well, if not so much my liner glazes. It was prone to bloating and fizzing/bubbling. In short, it can be finicky to work with. For unglazed work, well, that solves some of the problems! Still, watch for the bloat - bisque thoroughly and careful not to over fire. The reasons I'm replying (aside from Welcome!): a) an inch thick may be problematic. When you get to design and execution, maybe look into thinner sections, particularly when working with black clays. b) you might get brilliant white by glazing white stoneware, and/or applying slip or engobe to your white stoneware... c) some once fire aficionados/experts may chime in here - I'm not seeing any cons to once fire for unglazed ware. Be advised that dark/black clays typically require an extensive/thorough bisque to drive off all the bloaty stuff. Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 25, 2021 Report Share Posted October 25, 2021 Hi and welcome! I use Plainsman m390, which isn’t a black clay, but does tend to like slower firing cycles and a higher bisque. I tend to once fire things like ornaments or planters that have underglaze or engobe instead of glaze. I have a slow glaze cycle, so putting them in as filler isn’t a big deal, as long as the pieces are totally dry. In Calgary, that’s not a big issue, but depending on how humid a place you are in Ontario, it could be something to be mindful of. I agree with Tom that 1” is far too thick. Potential bloating issues aside, the finished product is going to be pretty heavy. Think 1 cm instead. Thick enough to be durable, but less weight to drag a tree branch down with. I haven’t worked with a lot of PSH, but I haven’t heard of any of them being particularly problematic. I don’t think porcelain deserves some of the bad rep it gets as a difficult material. As long as you have the ability to keep a bit of an eye on it as it dries to make sure it’s even, I don’t find most of the white-but-not-super-translucent porcelains drastically different to work with it over stoneware. Link to comment Share on other sites More sharing options...
Moh92 Posted October 25, 2021 Author Report Share Posted October 25, 2021 15 hours ago, Hulk said: Hi Moh! I haven't yet (and may never get around to it) tried working with porcelain, but have been through a bag of black (cone 5) clay. The black clay I tried fired to a very nice colour, smooth finish, and strong; it took several of my glazes well, if not so much my liner glazes. It was prone to bloating and fizzing/bubbling. In short, it can be finicky to work with. For unglazed work, well, that solves some of the problems! Still, watch for the bloat - bisque thoroughly and careful not to over fire. The reasons I'm replying (aside from Welcome!): a) an inch thick may be problematic. When you get to design and execution, maybe look into thinner sections, particularly when working with black clays. b) you might get brilliant white by glazing white stoneware, and/or applying slip or engobe to your white stoneware... c) some once fire aficionados/experts may chime in here - I'm not seeing any cons to once fire for unglazed ware. Be advised that dark/black clays typically require an extensive/thorough bisque to drive off all the bloaty stuff. Thank you for your time to reply, I appreciate it ! Great information and I feel better about the choice of the black clay. The the other points you mentioned : a) I already made some stoneware decorative objects with 0.5-1 inch thickness and had no problem with them at all. But since I'm changing to porcelein for the first time I was wondering if it will act the same way as stoneware in the kiln. My decorative pieces are not very complicated in design with minimal details and one of them is an infinity knot I attached a photo of it so you can get the idea. b) Glazing these kinds of pieces is not the right idea as you see the knot in the photo if I wanna glaze it I have to leave the bottom part of it unglazed which will look not right, parts of it are glazed and the other's are not. I haven't tried engobe yet but I'll give it a try. c)Good to hear that and will save me alot of money since I'm using someone else's kiln The decorative pieces I make are non functional as you see and if one firing is enough for the pieces to get the nice sturdiness and colour then that would be amazing. I'll try soon and see how it goes. I'm self taught and have limited access to studios where I live so excuse my lack of knowledge Link to comment Share on other sites More sharing options...
Moh92 Posted October 25, 2021 Author Report Share Posted October 25, 2021 14 hours ago, Callie Beller Diesel said: Hi and welcome! I use Plainsman m390, which isn’t a black clay, but does tend to like slower firing cycles and a higher bisque. I tend to once fire things like ornaments or planters that have underglaze or engobe instead of glaze. I have a slow glaze cycle, so putting them in as filler isn’t a big deal, as long as the pieces are totally dry. In Calgary, that’s not a big issue, but depending on how humid a place you are in Ontario, it could be something to be mindful of. I agree with Tom that 1” is far too thick. Potential bloating issues aside, the finished product is going to be pretty heavy. Think 1 cm instead. Thick enough to be durable, but less weight to drag a tree branch down with. I haven’t worked with a lot of PSH, but I haven’t heard of any of them being particularly problematic. I don’t think porcelain deserves some of the bad rep it gets as a difficult material. As long as you have the ability to keep a bit of an eye on it as it dries to make sure it’s even, I don’t find most of the white-but-not-super-translucent porcelains drastically different to work with it over stoneware. Thank you for sharing your experience ! I actually already made some decorative objects with 0.5-1 inch thickness as I mentioned in the other reply with a photo of one of the pieces. I used stoneware and had no issues. I'm just worried of porcelain may act differently in the kiln I usually keep my pieces to dry for 1-2 weeks in the studio and I make sure to keep it warm and dry with air circulation. I also weigh the pieces when bone dry so when they stop losing weight then I can tell that they are dry and good to go. I haven't tried engobe yet. I'll try sometime soon. Thank you again. I feel more confident now to try and see how it goes. Link to comment Share on other sites More sharing options...
Min Posted October 25, 2021 Report Share Posted October 25, 2021 46 minutes ago, Moh92 said: I'm just worried of porcelain may act differently in the kiln Porcelain when fired to maturity can definitely slump which could distort the shape. It can also stick to kiln shelves unless there is kiln wash on them. There is the risk the infinity knot rings you are making will slightly stick to each other where they touch. If you find this happens you can mix a little alumina hydrate with wax resist and brush it on where the 2 rings touch. A heaping teaspoon of alumina hydrate in about 1/2 cup wax resist is enough, it needs to be stirred often plus it's a good idea to put some food colouring in it so it doesn't get mixed up with regular wax resist. Once fired the alumina hydrate will just brush off the clay. (don't get any on glaze or you get a horrible rough surface) Dry the porcelain evenly to avoid it cracking, this usually means slowly under plastic. 46 minutes ago, Moh92 said: I also weigh the pieces when bone dry so when they stop losing weight then I can tell that they are dry and good to go. Try putting a piece of what you know is bone dry clay against your cheek. Then take a piece of clay that isn't bone dry and put it against your cheek, if it feels cooler then it still contains water. (both pieces from the same temperature room) 46 minutes ago, Moh92 said: I haven't tried engobe yet. I'll try sometime soon. Engobes (plus slips and underglazes) can whiten a surface but they won't give you the same beautiful finish a well vitrified porcelain can give. You aren't going to get translucent with pieces that thick though so perhaps that's not an issue. Link to comment Share on other sites More sharing options...
Morgan Posted October 26, 2021 Report Share Posted October 26, 2021 I have yet to find a black clay I love…either it is impossible to throw any sort of form with height or it does now take glazes great and is too much of a hassle to work with. that said I find Kentucky mudworks brown bear the closest one that does not bloat throws decent and takes glazes ok. Even though it’s dubbed brown it’s pretty much black in my eyes. I would love to find a black porcelain that is a good throwing body but have yet to. Black ice turns out just amazing but it is almost absurdly hard to throw…and I mean absurd. I have thrown more than a couple dozen of porcelain clays and even the ones that are difficult to throw do not even come close to black ice’s difficulty. It also comes so wet and soft you have to spend tons of time to even get it to a workable state. sorry for the rant but it drives me nuts because of how amazing it actually does turn out. Link to comment Share on other sites More sharing options...
Moh92 Posted October 27, 2021 Author Report Share Posted October 27, 2021 On 10/25/2021 at 2:00 PM, Min said: Porcelain when fired to maturity can definitely slump which could distort the shape. It can also stick to kiln shelves unless there is kiln wash on them. There is the risk the infinity knot rings you are making will slightly stick to each other where they touch. If you find this happens you can mix a little alumina hydrate with wax resist and brush it on where the 2 rings touch. A heaping teaspoon of alumina hydrate in about 1/2 cup wax resist is enough, it needs to be stirred often plus it's a good idea to put some food colouring in it so it doesn't get mixed up with regular wax resist. Once fired the alumina hydrate will just brush off the clay. (don't get any on glaze or you get a horrible rough surface) Dry the porcelain evenly to avoid it cracking, this usually means slowly under plastic. Try putting a piece of what you know is bone dry clay against your cheek. Then take a piece of clay that isn't bone dry and put it against your cheek, if it feels cooler then it still contains water. (both pieces from the same temperature room) Engobes (plus slips and underglazes) can whiten a surface but they won't give you the same beautiful finish a well vitrified porcelain can give. You aren't going to get translucent with pieces that thick though so perhaps that's not an issue. -AWESOME ! I really appreciate your time explaining stuff I didn't know. I just ordered Alumina hydrate and gonna use it with wax resist as you said just in case. -I forgot to mention that I use the cheek method to decide if the piece is dry or not lol -That is why I chose porcelain for the nicer finish it gives and yes, not having translucent is not an issue. Thanks again Link to comment Share on other sites More sharing options...
Moh92 Posted October 27, 2021 Author Report Share Posted October 27, 2021 On 10/26/2021 at 1:41 AM, Morgan said: I have yet to find a black clay I love…either it is impossible to throw any sort of form with height or it does now take glazes great and is too much of a hassle to work with. that said I find Kentucky mudworks brown bear the closest one that does not bloat throws decent and takes glazes ok. Even though it’s dubbed brown it’s pretty much black in my eyes. I would love to find a black porcelain that is a good throwing body but have yet to. Black ice turns out just amazing but it is almost absurdly hard to throw…and I mean absurd. I have thrown more than a couple dozen of porcelain clays and even the ones that are difficult to throw do not even come close to black ice’s difficulty. It also comes so wet and soft you have to spend tons of time to even get it to a workable state. sorry for the rant but it drives me nuts because of how amazing it actually does turn out. Thank you for sharing your experience and notes. The good thing with the pieces I'm making is that I won't use glazes on them and I'll leave the black clay as it is with the natural finish. I'm not going to make pots either, I'm just handbuilding small to medium pieces with minimal design and details so I think that will save me alot of time dealing with the difficulty of throwing it on the wheel lol I'll post another topic soon to share the final result Link to comment Share on other sites More sharing options...
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