If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
porcelain firing
In message , Steve Mills
writes 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. Dear Steve I'm working in Valentine's Audrey Blackman. I've tried other porcelain bodies and have found this the one that suits me best, so far. From Valentines' web site : "Audrey Blackman Porcelain Very Smooth This porcelain was developed for modelling and throwing using the finest materials available. Due to high plasticity this body is not suitable for casting and is only available in pugged form. Firing Range: 1220C-1280C (White and translucent)." I did try a small sample of southern ice, but much as I like the whiteness and purity of the fired clay, it wasn't the easiest to work with. I discovered the day before yesterday that I first worked in porcelain thirty years ago this year. I guess that means that I'm no spring dragon :-(((( ! Hope this helps with some sort of solution to my current problem. Look forward to hearing from you - and the others too. Thanks 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 |
Ads |
#12
|
|||
|
|||
porcelain firing
Susie wrote:
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 Silent but deadly....... |
#13
|
|||
|
|||
porcelain firing
This may help or may lead you into unknown problems. (Could apply that comment to any advice I suppose!) Bone china is biscuit fired to 1250 degC and above and is very prone to distortion. The glaze fire is at a much lower temperature. So in the biscuit firing the pieces are "bedded" in Alumina, what grade I don't know, I did ask about the firing of a lattice work basket that was about 6 inches high and I got the impression that it was pretty well immersed in alumina. This was about 20 years ago and it is not something I have direct experience of, so treat with caution! But it seems a reasonable starting point for some trials, the alumina should be reusable. I think that you need to experiment with some not so important pieces. Good Luck "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 |
#14
|
|||
|
|||
porcelain firing
An excellent solution Steve, but I would also caution her to dip the tips of
those supports in a bit of alumina so that the support doesn't stick to the piece. that can happen when the same clay body is used for both piece and support. Been there, done that. Best, Wayne Seidl "Steve Mills" wrote in message ... 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 |
#15
|
|||
|
|||
porcelain firing
interesting concept of total imersion of the piece into alumina. that
might work. i'd only add some concept to compensate for firing shrinkage would complete the idea. see ya steve On Oct 25, 2:36*pm, "Pierre Brayford" wrote: This may help or may lead you into unknown problems. (Could apply that comment to any advice I suppose!) Bone china is biscuit fired to 1250 degC and above and is very prone to distortion. The glaze fire is at a much lower temperature. So in the biscuit firing the pieces are "bedded" in Alumina, what grade I don't know, I did ask about the firing of a lattice work basket that was about 6 inches high and I got the impression that it was pretty well immersed in alumina. This was about 20 years ago and it is not something I have direct experience of, so treat with caution! But it seems a reasonable starting point for some trials, the alumina should be reusable. I think that you need to experiment with some not so important pieces. Good Luck"Susie Thompson" wrote in .uk... 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- Hide quoted text -- Show quoted text - |
#16
|
|||
|
|||
porcelain firing
|
#17
|
|||
|
|||
porcelain firing
i've simply monitored all this, but the concept hit me from a different
application. maybe it might spark an idea. my wife got LONG ago some silica that she'd pour into a shoebox over some fresh picked flowers (mini roses were her favorite). cover the flowers with silica & let them sit for several weeks. the silica would cover the flower & grains get in here & there. the flowers would dry out & she'd shake them gently to release the silica. save the silica & do more flowers. so, a high temp material could do the same thing i would guess? high temp alumina sand? but to apply the flower concept to clay means a shrink element is now included. so a high temp silica sand that shrinks? i don't know how to do that unless this magic high temp sand had something in it to burn out & *shrink* some as well? i bet maybe very fine saw dust could be blended in that special ratio (and what's that?!) and the sand mix would shrink the same-similar to the art piece. ~ except the saw dust would melt & turn the support structure into a clump. perhaps the sand mix accidently lets a piece shrink within it to not hurt anything? very interesting challenge. i don't know if there is anything that has a property analogus to foam at high temperatures. a magic sand that reacts like shreaded foam? vermiculite? that's kind of foamy in feel. how big is this thing? maybe at a small size it's ok. "large" and shrinkage becomes a problem. see ya steve On Oct 28, 8:24*am, Susie wrote: In message .com, "steve * " writes interesting concept of total imersion of the piece into alumina. *that might work. *i'd only add some concept to compensate for firing shrinkage would complete the idea. steve On Oct 25, 2:360 This may help or may lead you into unknown problems. (Could apply that comment to any advice I suppose!) Bone china is biscuit fired to 1250 degC and above and is very prone to distortion. The glaze fire is at a much lower temperature. So in the biscuit firing the pieces are "bedded" in Alumina, what grade I don't know, I did ask about the firing of a lattice work basket that was about 6 inches high and I got the impression that it was pretty well immersed in alumina. This was about 20 years ago and it is not something I have direct experience of, so treat with caution! But it seems a reasonable starting point for some trials, the alumina should be reusable. I think that you need to experiment with some not so important pieces.I've been following all your suggestions - thanks for all your ideas for future projects. * I've worked with porcelain for a long time - see previous post - but I've never made anything quite so ambitious before. I'm wondering just what the limits of porcelain are? * I've used ceramic fibre and sacrificial props for supporting all sorts of things in the past, and in general they've worked fine. *However, this time it's got far beyond the point I've ever tried before. *I just built the dragons without thinking about how I would fire them - hence my current problems! Regarding immersing in alumina, I presume you have some sort of saggar/box/container in which you place the object and then gently fill with alumina. *How on earth can you tell if the weight of the alumina has damaged the unfired work as you bury it? *In porcelain, I don't know if you can high biscuit fire and then apply glaze at a lower temperature as per bone china. I've tried working in bone china, but unless the body has changed, I found it difficult and un-cooperative. *Think I'll stick to porcelain. If the weather's better tomorrow I'm going to put the dragons in the kiln and fire them very slowly up to around 1050C, to check for problems/cracks/etc showing at lower temperature. *If they survive that, maybe I'll be able to get ceramic fibre around and under the crucial bits before I fire them up to 1240C, the lowest recommended firing temperature for the clay. I'll take some photos in the morning before hand, in case of disaster. It's be good to remember just what I made, even if the dragons come to earth with a *crash. Thanks all 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- Hide quoted text -- Show quoted text - |
#18
|
|||
|
|||
porcelain firing
If it is truly a high fire material and does not have any waste in it
(water, carbon, etc. that comes of at a low temp) it is not going to shrink is it? And since it is fine grained should it not act very much like water? That is as the clay object within the container shrinks, the grains are simply going to fill in and the level of all will lower in the container. I am of course assuming that the object and the high fire material are in a saggar or some type of container. Am I misunderstanding? (probably). Donna """""""""""""""""""""""""""""""""""""""""""""""""" """"""""""""""""""" wrote in message ups.com... i've simply monitored all this, but the concept hit me from a different application. maybe it might spark an idea. my wife got LONG ago some silica that she'd pour into a shoebox over some fresh picked flowers (mini roses were her favorite). cover the flowers with silica & let them sit for several weeks. the silica would cover the flower & grains get in here & there. the flowers would dry out & she'd shake them gently to release the silica. save the silica & do more flowers. so, a high temp material could do the same thing i would guess? high temp alumina sand? but to apply the flower concept to clay means a shrink element is now included. so a high temp silica sand that shrinks? i don't know how to do that unless this magic high temp sand had something in it to burn out & *shrink* some as well? i bet maybe very fine saw dust could be blended in that special ratio (and what's that?!) and the sand mix would shrink the same-similar to the art piece. ~ except the saw dust would melt & turn the support structure into a clump. perhaps the sand mix accidently lets a piece shrink within it to not hurt anything? very interesting challenge. i don't know if there is anything that has a property analogus to foam at high temperatures. a magic sand that reacts like shreaded foam? vermiculite? that's kind of foamy in feel. how big is this thing? maybe at a small size it's ok. "large" and shrinkage becomes a problem. see ya steve """"""""""""""""""" """""""""""""""""""""""""""""""""""""""""""""""""" """"""""""""""""""""""""""" |
#19
|
|||
|
|||
porcelain firing
the vitrification occuring is what causes the shrinkage when you head
up to cone 10. the 1st shrinkage you see if from wet to dry. the second shrink you see if from dry to fully vitrified. the spaces between all the little grains of clay close up tighter. so you will see some more shrinkage in that last fire. see ya steve On Oct 28, 10:18*am, "DKat" wrote: If it is truly a high fire material and does not have any waste in it (water, carbon, etc. that comes of at a low temp) it is not going to shrink is it? *And since it is fine grained should it not act very much like water? That is as the clay object within the container shrinks, the grains are simply going to fill in and the level of all will lower in the container. *I am of course assuming that the object and the high fire material are in a saggar or some type of container. *Am I misunderstanding? *(probably). Donna """""""""""""""""""""""""""""""""""""""""""""""""" wrote in oglegroups.com... i've simply monitored all this, but the concept hit me from a different application. *maybe it might spark an idea. my wife got LONG ago some silica that she'd pour into a shoebox over some fresh picked flowers (mini roses were her favorite). *cover the flowers with silica & let them sit for several weeks. *the silica would cover the flower & grains get in here & there. *the flowers would dry out & she'd shake them gently to release the silica. *save the silica & do more flowers. so, a high temp material could do the same thing i would guess? *high temp alumina sand? but to apply the flower concept to clay means a shrink element is now included. *so a high temp silica sand that shrinks? *i don't know how to do that unless this magic high temp sand had something in it to burn out & *shrink* some as well? *i bet maybe very fine saw dust could be blended in that special ratio (and what's that?!) and the sand mix would shrink the same-similar to the art piece. *~ except the saw dust would melt & turn the support structure into a clump. perhaps the sand mix accidently lets a piece shrink within it to not hurt anything? very interesting challenge. i don't know if there is anything that has a property analogus to foam at high temperatures. *a magic sand that reacts like shreaded foam? vermiculite? *that's kind of foamy in feel. how big is this thing? *maybe at a small size it's ok. *"large" and shrinkage becomes a problem. see ya steve *""""""""""""""""""" """""""""""""""""""""""""""""""""""""""""""""""""" """""""""""""""""""""""""*"" |
#20
|
|||
|
|||
porcelain firing
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
FAQ Raku part 2 of 2 | SBRANFPOTS | Pottery | 0 | October 21st 03 02:13 PM |
FAQ Raku part 2 of 2 | SBRANFPOTS | Pottery | 0 | September 16th 03 11:11 PM |
Firing Tmes | David Coggins | Pottery | 0 | September 1st 03 08:27 AM |
Raku FAQs | Tom Buck | Pottery | 0 | July 20th 03 04:49 AM |
FAQ:Intro to rec.crafts.pottery | Mishy Lowe | Pottery | 0 | July 18th 03 06:05 AM |