A crafts forum. CraftBanter

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.

Go Back   Home » CraftBanter forum » Craft related newsgroups » Pottery
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

porcelain firing



 
 
Thread Tools Display Modes
  #1  
Old October 24th 06, 11:57 AM posted to rec.crafts.pottery
Susie Thompson
external usenet poster
 
Posts: 7
Default 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
Ads
  #2  
Old October 24th 06, 03:43 PM posted to rec.crafts.pottery
DKat
external usenet poster
 
Posts: 99
Default 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  
Old October 24th 06, 04:50 PM posted to rec.crafts.pottery
Susie
external usenet poster
 
Posts: 26
Default 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  
Old October 24th 06, 08:13 PM posted to rec.crafts.pottery
DKat
external usenet poster
 
Posts: 99
Default 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  
Old October 24th 06, 08:48 PM posted to rec.crafts.pottery
Susie
external usenet poster
 
Posts: 26
Default 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  
Old October 24th 06, 10:43 PM posted to rec.crafts.pottery
Eddie Daughton
external usenet poster
 
Posts: 11
Default 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  
Old October 24th 06, 11:15 PM posted to rec.crafts.pottery
DKat
external usenet poster
 
Posts: 141
Default 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  
Old October 25th 06, 01:03 AM posted to rec.crafts.pottery
Steve Mills
external usenet poster
 
Posts: 49
Default 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  
Old October 25th 06, 10:30 AM posted to rec.crafts.pottery
Susie
external usenet poster
 
Posts: 26
Default 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  
Old October 25th 06, 12:07 PM posted to rec.crafts.pottery
Steve Mills
external usenet poster
 
Posts: 49
Default 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
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

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


All times are GMT +1. The time now is 08:01 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 CraftBanter.
The comments are property of their posters.