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#1
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porcelain firing
I've built something which is very, very fragile. It will finally need
firing to 1250C to mature the clay - at which point I suspect that the clay will be beginning to 'soften' and not be able to take its own weight. What I need to do is to biscuit fire to a sufficiently high enough temperature so that I can safely tuck ceramic fibre in/under certain areas to support the clay at 1250C. If I biscuit fire under 1000C, which is what I usually do with most things so that I can check for cracks, etc, the clay will still be too fragile/brittle to allow me anywhere near. So, how high can I take it to have enough strength? This is unknown territory for me. Help, please. Susie ps I hope that soon I'll have a website so that I can post images of the things I make that give me this sort of problem/headache/learning curve! -- Susie Thompson If you can't stand the heat, don't tickle the dragon to email me replace "deadspam.com" with susiethompson.co.uk |
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#2
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porcelain firing
If it is so fragile (I assume you mean thin), why would its weight, firing
it to a mature temperature, be a problem? As long as you are not firing beyond the clays' range, I have never seen any clay collapse, melt, etc. from its weight. You could bisque fire to about 1046 and that would make it less porous, weak. Are you going to glaze this piece? If not, I would pass on the bisque fire all together. Just my 2 cents. "Susie Thompson" wrote in message ... I've built something which is very, very fragile. It will finally need firing to 1250C to mature the clay - at which point I suspect that the clay will be beginning to 'soften' and not be able to take its own weight. What I need to do is to biscuit fire to a sufficiently high enough temperature so that I can safely tuck ceramic fibre in/under certain areas to support the clay at 1250C. If I biscuit fire under 1000C, which is what I usually do with most things so that I can check for cracks, etc, the clay will still be too fragile/brittle to allow me anywhere near. So, how high can I take it to have enough strength? This is unknown territory for me. Help, please. Susie ps I hope that soon I'll have a website so that I can post images of the things I make that give me this sort of problem/headache/learning curve! -- Susie Thompson If you can't stand the heat, don't tickle the dragon to email me replace "deadspam.com" with susiethompson.co.uk |
#3
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porcelain firing
In message , DKat
writes If it is so fragile (I assume you mean thin), why would its weight, firing it to a mature temperature, be a problem? As long as you are not firing beyond the clays' range, I have never seen any clay collapse, melt, etc. from its weight. You could bisque fire to about 1046 and that would make it less porous, weak. Are you going to glaze this piece? If not, I would pass on the bisque fire all together. Just my 2 cents. I'm talking about flying dragons with horizontal and vertical outstretched wings, tails etc. Unfired, the height of the main dragon is about eight inches from claw to top of its vertical wing, with no support. The plan is that when fired the wings and a lot of the detail become translucent. I need to pack ceramic fibre under the dragons' "arm pits" and other bits and pieces to support the wings, etc as well as under their heads and necks to stop them collapsing too far. No, I'm not glazing it, which takes out some of the complications that could have happened. I I suppose that I could under fire and make sure, but after a lot of work I'm trying to make sure that this comes out as intended and not dragons with the droops! Susie -- Susie Thompson If you can't stand the heat, don't tickle the dragon! to email me, replace deadspam.com with susiethompson.co.uk |
#4
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porcelain firing
Ahhh, becomes clearer. The experience I have in this regard is with very
large platters with a small foot and there is an issue of the droop you mention. If you are not glazing and you are not going so high that you risk the clay itself melting, I would make clay support pillars of various heights to use both for the bisque and the highfire or just fire once. You could also use kiln supports. Using fabric is going to leave you with the same problem of the wings flattening out I would think. Even for the bisque my platters need support. Are you working with paper clay or are the wings so terribly thin that they cannot risk 'handling' until highfired? Again, just my 2 cents. The platters I make are around 27" and are heavy. Clay wads are placed around the edges. "Susie" wrote in message ... In message , DKat writes If it is so fragile (I assume you mean thin), why would its weight, firing it to a mature temperature, be a problem? As long as you are not firing beyond the clays' range, I have never seen any clay collapse, melt, etc. from its weight. You could bisque fire to about 1046 and that would make it less porous, weak. Are you going to glaze this piece? If not, I would pass on the bisque fire all together. Just my 2 cents. I'm talking about flying dragons with horizontal and vertical outstretched wings, tails etc. Unfired, the height of the main dragon is about eight inches from claw to top of its vertical wing, with no support. The plan is that when fired the wings and a lot of the detail become translucent. I need to pack ceramic fibre under the dragons' "arm pits" and other bits and pieces to support the wings, etc as well as under their heads and necks to stop them collapsing too far. No, I'm not glazing it, which takes out some of the complications that could have happened. I I suppose that I could under fire and make sure, but after a lot of work I'm trying to make sure that this comes out as intended and not dragons with the droops! Susie -- Susie Thompson If you can't stand the heat, don't tickle the dragon! to email me, replace deadspam.com with susiethompson.co.uk |
#5
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porcelain firing
In message , DKat
writes Ahhh, becomes clearer. The experience I have in this regard is with very large platters with a small foot and there is an issue of the droop you mention. If you are not glazing and you are not going so high that you risk the clay itself melting, I would make clay support pillars of various heights to use both for the bisque and the highfire or just fire once. You could also use kiln supports. Using fabric is going to leave you with the same problem of the wings flattening out I would think. Even for the bisque my platters need support. Are you working with paper clay or are the wings so terribly thin that they cannot risk 'handling' until highfired? Again, just my 2 cents. The platters I make are around 27" and are heavy. Clay wads are placed around the edges. I suppose that I really should be replying with my 2 pence worth ;-))) It's a sculpture of two squabbling dragons hatched and hatching out of eggs. I cannot go anywhere near this thing until it is high fired; as you guess the wings and much of the detail is very fine indeed. I do sometimes work with porcelain paper clay, but this one is made in plain porcelain as I find that it's difficult to get fine detail and 'clean edges' with paper clay. It's been too complicated a thing to be able to build supports in as I made it, mostly because I don't think that I would be able to get them out after firing without risking disaster. This is why I want find out just how high I can fire the porcelain without risking slumping, then packing them carefully with ceramic fibre and re-firing to top temperature at around 1250. IF and it's a bit of a big IF, my dragons survive this, I'll take some pics and try to get around to posting where you can see just what this is all about. On second thoughts, I'm going to take pics before I fire them, just in case. There seems to be some sort of justice, dragons emerging from 1250C with their wings flying!! Or not :-(((( Here's hoping Regards Susie -- Susie Thompson If you can't stand the heat, don't tickle the dragon! to email me, replace deadspam.com with susiethompson.co.uk |
#6
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porcelain firing
Susie wrote:
In message , DKat writes Ahhh, becomes clearer. The experience I have in this regard is with very large platters with a small foot and there is an issue of the droop you mention. If you are not glazing and you are not going so high that you risk the clay itself melting, I would make clay support pillars of various heights to use both for the bisque and the highfire or just fire once. You could also use kiln supports. Using fabric is going to leave you with the same problem of the wings flattening out I would think. Even for the bisque my platters need support. Are you working with paper clay or are the wings so terribly thin that they cannot risk 'handling' until highfired? Again, just my 2 cents. The platters I make are around 27" and are heavy. Clay wads are placed around the edges. I suppose that I really should be replying with my 2 pence worth ;-))) It's a sculpture of two squabbling dragons hatched and hatching out of eggs. I cannot go anywhere near this thing until it is high fired; as you guess the wings and much of the detail is very fine indeed. I do sometimes work with porcelain paper clay, but this one is made in plain porcelain as I find that it's difficult to get fine detail and 'clean edges' with paper clay. It's been too complicated a thing to be able to build supports in as I made it, mostly because I don't think that I would be able to get them out after firing without risking disaster. This is why I want find out just how high I can fire the porcelain without risking slumping, then packing them carefully with ceramic fibre and re-firing to top temperature at around 1250. IF and it's a bit of a big IF, my dragons survive this, I'll take some pics and try to get around to posting where you can see just what this is all about. On second thoughts, I'm going to take pics before I fire them, just in case. There seems to be some sort of justice, dragons emerging from 1250C with their wings flying!! Or not :-(((( Here's hoping Regards Susie Just to put my five eggs in... How about supporting the dragone UPSIDE down for the firing so that if they slump they'll slump upwards (if you see what i mean???) could be a new way of getting that inaudible lightness of being that comes from dragons.... Hugs Eddie |
#7
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porcelain firing
It sounds so very beautiful! Have you posted on clayart? They have a much
larger audience and it is more likely that someone who does this type of work might reply. When I add my 2 cents I mean that I am giving information that is entirely guess work and should be taken with a very large grain of salt (I just love these idioms...). I really wish you luck and all the good will of the kiln gods. Please post pictures (I'm very fond of dragons). Donna "Susie" wrote in message ... In message , DKat writes Ahhh, becomes clearer. The experience I have in this regard is with very large platters with a small foot and there is an issue of the droop you mention. If you are not glazing and you are not going so high that you risk the clay itself melting, I would make clay support pillars of various heights to use both for the bisque and the highfire or just fire once. You could also use kiln supports. Using fabric is going to leave you with the same problem of the wings flattening out I would think. Even for the bisque my platters need support. Are you working with paper clay or are the wings so terribly thin that they cannot risk 'handling' until highfired? Again, just my 2 cents. The platters I make are around 27" and are heavy. Clay wads are placed around the edges. I suppose that I really should be replying with my 2 pence worth ;-))) It's a sculpture of two squabbling dragons hatched and hatching out of eggs. I cannot go anywhere near this thing until it is high fired; as you guess the wings and much of the detail is very fine indeed. I do sometimes work with porcelain paper clay, but this one is made in plain porcelain as I find that it's difficult to get fine detail and 'clean edges' with paper clay. It's been too complicated a thing to be able to build supports in as I made it, mostly because I don't think that I would be able to get them out after firing without risking disaster. This is why I want find out just how high I can fire the porcelain without risking slumping, then packing them carefully with ceramic fibre and re-firing to top temperature at around 1250. IF and it's a bit of a big IF, my dragons survive this, I'll take some pics and try to get around to posting where you can see just what this is all about. On second thoughts, I'm going to take pics before I fire them, just in case. There seems to be some sort of justice, dragons emerging from 1250C with their wings flying!! Or not :-(((( Here's hoping Regards Susie -- Susie Thompson If you can't stand the heat, don't tickle the dragon! to email me, replace deadspam.com with susiethompson.co.uk |
#8
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porcelain firing
In article , Susie Thompson
writes I've built something which is very, very fragile. It will finally need firing to 1250C to mature the clay - at which point I suspect that the clay will be beginning to 'soften' and not be able to take its own weight. Dear Susie A common solution to this sort of problem is to make a number of conical supports out of the same clay so as to match shrinkage etc. These are usually called sacrificial props. the tip of each prop is pointed, so as to leave as little evidence as possible of its use after firing has taken place. This technique is generally used when the piece is to be glazed, but has a lot of merit in unglazed use! Steve -- Steve Mills Bath UK |
#9
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porcelain firing
In message , Steve Mills
writes A common solution to this sort of problem is to make a number of conical supports out of the same clay so as to match shrinkage etc. These are usually called sacrificial props. the tip of each prop is pointed, so as to leave as little evidence as possible of its use after firing has taken place. This technique is generally used when the piece is to be glazed, but has a lot of merit in unglazed use! Dear Steve and Donna and Ed Thanks for all your suggestions and ideas. Ed, can you explain "getting that inaudible lightness of being that comes from dragons ..."? Please. I agree that dragons must have "lightness of being" as well as great speed - you don't often manage to see one ;-) As for the "inaudible" bit, well I read somewhere that dragons' flight is methane or baked bean powered;-))) I just can't imagine that being silent flight! I guess that if I fired my dragons upside down, then they would fall to earth in a shambolic heap. Donna, dragons seem to be part of a global consciousness and most folks seem to respond to them. They only got a bad press owing to a certain strain of dragon having a partiality for maidens and then being skewered by knights in armour. Glad you like dragons too and thanks for your good wishes. Steve, if only. If this thing survives I will be so relieved. I've used sacrificial props many times in the past and they really do work. However, this time it's not feasible. I think I'm going to try firing to somewhere around 1150- 1180 to gain body strength and then surround and pack it with ceramic fibre. The only thing I'm not sure about (not been through college and have no great technical knowledge) is if at some point I risk accidentally hitting one of the crucial temperatures in a firing and mess the whole thing up through ignorance. Confirmation that my plan will/won't work would be really welcome. It's been drying very slowly for a couple of weeks now, and is finally out in open air for a final dry out. I reckon I'll be firing it over this coming weekend. Best wishes and thanks to you all Will keep you up to date with developments. Susie -- Susie Thompson If you can't stand the heat, don't tickle the dragon! to email me, replace deadspam.com with susiethompson.co.uk |
#10
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porcelain firing
In article , Susie
writes Dear Steve and Donna and Ed Thanks for all your suggestions and ideas. Dear Susie, Out of interest; could you tell me which Porcelain body you are using for this project? I was involved in supplying UK Ceramic materials for a while until recently, so have some knowledge (and interest) in their performance. Steve -- Steve Mills Bath UK |
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