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.

In message , DKat writes

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

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.

In message , DKat writes

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

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

In article , Susie Thompson 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!

Steve

In message , Steve Mills writes

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

In article , Susie writes

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

In message , Steve Mills writes

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

Silent but deadly.......

This may help or may lead you into unknown problems. (Could apply that comment to any advice I suppose!)

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

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

snipped-for-privacy@arrandragons.demon.co.uk...

d text -- Show quoted text -

In message , "steve snipped-for-privacy@aol.com" writes

apply that

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

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

(Could apply that

I've been following all your suggestions - thanks for all your ideas for

ext -- Show quoted text -

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

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 """"""""""""""""""" """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

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

glegroups.com...

Steve, Your post has jogged a memory; Doll makers both here and on your side of the pond fire the heads embedded in Silica Sand. Maybe this would work with Susie's Piece. In addition I ran Susie's fibre technique past a Potter/Sculptor friend who confirmed that it will work well and the only clean-up technique needed would possibly be with a bit of fine sandpaper.

Steve Bath UK

In article , steve snipped-for-privacy@aol.com writes

work. 0 >> >shrinkage would complete the idea.

ambitious before.

sacrificial props for supporting all sorts of things in the

tried before. 0 >> without thinking about how I would fire them - hence my current

can high biscuit fire and then apply glaze at a lower temperature

get ceramic fibre around and under the crucial