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porcelain firing



 
 
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  #11  
Old October 25th 06, 12:45 PM posted to rec.crafts.pottery
Susie
external usenet poster
 
Posts: 26
Default 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
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  #12  
Old October 25th 06, 06:10 PM posted to rec.crafts.pottery
Eddie Daughton
external usenet poster
 
Posts: 11
Default 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  
Old October 25th 06, 10:36 PM posted to rec.crafts.pottery
Pierre Brayford
external usenet poster
 
Posts: 5
Default 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  
Old October 25th 06, 10:38 PM posted to rec.crafts.pottery
WJ Seidl
external usenet poster
 
Posts: 5
Default 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  
Old October 27th 06, 02:04 AM posted to rec.crafts.pottery
steve [email protected]
external usenet poster
 
Posts: 43
Default 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  
Old October 28th 06, 04:24 PM posted to rec.crafts.pottery
Susie
external usenet poster
 
Posts: 26
Default porcelain firing

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
  #17  
Old October 28th 06, 05:50 PM posted to rec.crafts.pottery
steve [email protected]
external usenet poster
 
Posts: 43
Default 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  
Old October 28th 06, 07:18 PM posted to rec.crafts.pottery
DKat
external usenet poster
 
Posts: 141
Default 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  
Old October 29th 06, 05:13 PM posted to rec.crafts.pottery
steve [email protected]
external usenet poster
 
Posts: 43
Default 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  
Old October 30th 06, 12:53 AM posted to rec.crafts.pottery
Steve Mills
external usenet poster
 
Posts: 49
Default porcelain firing

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 . com, steve
writes
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, 8:240 In message .com,
"steve 0




interesting concept of total imersion of the piece into alumina. 0 might work. 0 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. 0 previous post - but I've never made anything quite so ambitious before.
I'm wondering just what the limits of porcelain are? 0 fibre and sacrificial props for supporting all sorts of things in the
past, and in general they've worked fine. 0 far beyond the point I've ever tried before. 0 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. 0 has damaged the unfired work as you bury it? 0 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. 0
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. 0 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 0
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 -


--
Steve Mills
Bath
UK
 




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