Susan H. Park on wed 27 aug 97
Does anyone out there in clay land have experience with Bone China
casting? There was a terrific article on it recently and they mentioned
an ingredient called "Dispex". Is this a deflocculant? Is it available
on the PNW coast of N America?
As always - thanks for taking the time to share!
Susan in Seattle
Tony Hansen on fri 29 aug 97
Displex is a polyelectrolyte deflocculant, similar to Darvan I believe.
Manufacturers claim that in comparison to the conventional soda
ash-sodium silicate system, these
polyelectrolytes produce slips with longer casting range, higher solids
content, improved viscosity stability, fewer "soda" or "hard spots",
and significantly increased mold life. Slips also tend to reclaim better
without the need for constant adjustments with more deflocculant
(although
my experience is that you do often need to add more deflocculant to
maintain the slip).
--
T o n y H a n s e n, I M C thansen@digitalfire.com
=========================================================
INSIGHT5/Magic of Fire II demos at http://digitalfire.com
stevemills on fri 29 aug 97
Sodium Dispex is a defloccculant and VERY powerful, a little goes a long
way. There is a superb book on slipcasting by Sasha Wardell who is a
brilliant caster in Bone China herself. Publisher:A & C Black, Ceramic
Handbook series,ISBN:0-7136-4067-7, title:Slipcasting.
Steve.
In message , "Susan H. Park" writes
>----------------------------Original message----------------------------
>Does anyone out there in clay land have experience with Bone China
>casting? There was a terrific article on it recently and they mentioned
>an ingredient called "Dispex". Is this a deflocculant? Is it available
>on the PNW coast of N America?
>
>As always - thanks for taking the time to share!
>
>Susan in Seattle
>
--
Steve Mills
@Bath Potters Supplies
Dorset Close
Bath
BA2 3RF
UK
Tel:(44) (0)1225 337046
Fax:(44) (0)1225 462712
Jaana Rasanen on tue 17 mar 98
I'm trying to make my own bone china, but having some problems:
difficulties to find right kind of plaster for casting (the clay stics to
the mold and eats the mold very fast) and finding right kind of
deflokkulants.
If you know anything about bone china (calsinating the bones,
clayformulas, glazing and temprature, partical size of boneash etc.),
please help me! All kinds of information is valuable.
Thank You for Your time,
Jaana
Louis Katz on wed 18 mar 98
Kurt Weiser had some success with a fake Bone China fired around cone 5
using Zinc Borate as a flux.It had a beautiful softness.
Zinc Borate is used as a fire proofing agent. There was an article a few
years back on it. I suspect that it was in 1988-or 89 .
Jeff Lawrence on wed 18 mar 98
> Jaana Rasanen wrote:
>I'm trying to make my own bone china, but having some problems:
>difficulties to find right kind of plaster for casting (the clay stics to
>the mold and eats the mold very fast) and finding right kind of
>deflokkulants.
Hello Jaana,
I know nothing about bone china, but I am expert at making bad molds.
Sometimes, when I use too much water in the plaster, I get bad release (clay
sticks) and the mold wears away very fast. If I were you, I would try making
another mold with less water (use manufacturer's suggested ratio).
Another trick of mine is too much watery soap on the model when I pour. This
can make the surface very weak and it gets eaten away in no time.
One more possibility: a plaster salesman for United States Gypsum said they
have a new plaster called Duramold which lasts twice as long as their usual.
Perhaps your local company has a comparable product.
good luck
Jeff
Jeff Lawrence
jml@sundagger.com
Sun Dagger Design
Rt 3 Box 220
Espanola, NM 87532
ph 505-753-5913
Grace Liu on wed 1 apr 98
One tip about making your moulds. Try brushing lacquer on the original
model & let dry before pouring the plaster (instead of using a watery
soap solution).
For bone china clay and glaze formulas, see if you can get your hands on
James Chappell's The Potter's Complete Book of Clay and Glazes. Has a
chapter on porcelain clay formulas some of which contain bone ash. And
there are many more glaze formulas for porcelain. It's a rather
expensive book, but well worth it for its wealth of information.
grace
Jeff Lawrence wrote:
>
> ----------------------------Original message----------------------------
> > Jaana Rasanen wrote:
> >I'm trying to make my own bone china, but having some problems:
> >difficulties to find right kind of plaster for casting (the clay stics to
> >the mold and eats the mold very fast) and finding right kind of
> >deflokkulants.
>
> Hello Jaana,
>
> I know nothing about bone china, but I am expert at making bad molds.
>
> Sometimes, when I use too much water in the plaster, I get bad release (clay
> sticks) and the mold wears away very fast. If I were you, I would try making
> another mold with less water (use manufacturer's suggested ratio).
>
> Another trick of mine is too much watery soap on the model when I pour. This
> can make the surface very weak and it gets eaten away in no time.
>
> One more possibility: a plaster salesman for United States Gypsum said they
> have a new plaster called Duramold which lasts twice as long as their usual.
> Perhaps your local company has a comparable product.
>
> good luck
> Jeff
> Jeff Lawrence
> jml@sundagger.com
> Sun Dagger Design
> Rt 3 Box 220
> Espanola, NM 87532
> ph 505-753-5913
Eric Newman on thu 13 nov 03
I am exploring the possibility of developing a throwable bone china clay
body. I have read much that states they are both un-plastic and that they
have minimal mechanical strength when bone dry. Does anyone have
experience with this (so I don't repeat your mistakes)? I am thinking of
adding a small percentage of VeeGum Cer to counteract these problems, but
am concerned about reported tendencies to spoil (but this may just be in
glazes, not clay bodies). Other suggestions or comments would be welcome.
Many thanks in advance.
Eric
Janet Kaiser on fri 14 nov 03
Dear Eric Newman
PLEASE have a decko in the Clayart archives... I wrote out a huge
wad of "historical" stuff about bone china not so long ago and
(not least) as it went without any acknowledgement whatsoever
from the questioner, I have no inclination to type it out again!
Just type "bone china" into the search and you will get lot of
information including some indication of what not to do!
All the best - please report to the list what you try and how it
works out!
Janet Kaiser
*** IN REPLY TO THE FOLLOWING MAIL:
>I am exploring the possibility of developing a throwable bone
china clay
>body. I have read much that states they are both un-plastic and
that they
>have minimal mechanical strength when bone dry. Does anyone
have
>experience with this (so I don't repeat your mistakes)? I am
thinking of
>adding a small percentage of VeeGum Cer to counteract these
problems, but
>am concerned about reported tendencies to spoil (but this may
just be in
>glazes, not clay bodies). Other suggestions or comments would
be welcome.
*** THE MAIL FROM Eric Newman ENDS HERE ***
***********************************************************
The top posted mail was sent by Janet Kaiser
The Chapel of Art : Capel Celfyddyd
8 Marine Crescent : Criccieth : Wales : UK
Centre of Excellence for The Arts
Home of The International Potters' Path
Tel: ++44 (01766) 523570 http://www.the-coa.org.uk
Open: 13.00 to 17.00hrs : Tuesday to Saturday
************** AVG Virus Protected ********************
Eric Newman on sat 15 nov 03
Janet,
Thank you for responding. I had already read your earlier posting and
appreciated its historicity. But I'm trying to develop a throwable body
and I am having difficulty finding anything that addresses fixing the
problems beyond stating what they are (non-plasticity and poor mechanical
strength). So far, after a month of aging, tho' it is the shortest when
wedging, I am having the best throwing from a body: 25 Cornish Stone, 25
6-Tile Kaolin, 50 Bone ash with added 5 bentonite. Variations that are
less good for throwing (but this is all very preliminary) because they tend
to slump at the base as you pull up include substituting 10 Talc for 10
Bone ash, and substituting 10 Ball clay for 10 Kaolin. They are more
plastic, however. I'm waiting to hear back from the manufacturer about the
VeeGum and I'm thinking about adding some molochite (from the same body)
for tooth.
Eric
Janet Kaiser on sun 16 nov 03
You are welcome, Eric! I am certainly not the one to help you
further on this though! Ron Roy and others who monitor this list
are better placed to advise as their jobs include formulating and
making clay!
Perhaps if you explained more precisely what you want to achieve
they will add their 2 cents worth? I think that throwable "bone
china" (as in grandma's best dinner service) is not going to be
possible or achievable given that the making is the least of the
problems and the firing will be the real crunch... I envision
little puddles of molten clay stuck to the kiln bats for
eternity... But I could be so wrong!
I admire individuals like you who beaver away trying out
different or new approaches. After all, we would not have the
electric light bulb or rocket propulsion without "garage
inventors". However... If you could just explain the *qualities*
of the clay body you are attempting to formulate beyond "bone
china" it would maybe kick-start others in applying their
intellects to the possibilities?
Just my two pence worth! :o)
Sincerely
Janet Kaiser -- Loving every page of Michael Moore's latest
book... What a great American patriot!
*** IN REPLY TO THE FOLLOWING MAIL:
>snip>and I am having difficulty finding anything that addresses
fixing the
>problems beyond stating what they are (non-plasticity and poor
mechanical
>strength). So far, after a month of aging, tho' it is the
shortest when
>wedging, I am having the best throwing from a body: 25 Cornish
Stone, 25
>6-Tile Kaolin, 50 Bone ash with added 5 bentonite. Variations
that are
>less good for throwing (but this is all very preliminary)
because they tend
>to slump at the base as you pull up include substituting 10 Talc
for 10
>Bone ash, and substituting 10 Ball clay for 10 Kaolin. They are
more
>plastic, however. I'm waiting to hear back from the
manufacturer about the
>VeeGum and I'm thinking about adding some molochite (from the
same body)
>for tooth.
*** THE MAIL FROM Eric Newman ENDS HERE ***
***********************************************************
The top posted mail was sent by Janet Kaiser
The Chapel of Art : Capel Celfyddyd
8 Marine Crescent : Criccieth : Wales : UK
Centre of Excellence for The Arts
Home of The International Potters' Path
Tel: ++44 (01766) 523570 http://www.the-coa.org.uk
Open: 13.00 to 17.00hrs : Tuesday to Saturday
************** AVG Virus Protected ********************
Eric Newman on sun 16 nov 03
Janet, what a good idea!
OK, I guess what first got me interested in developing a "throwable bone
china" was the challenge. I couldn't find any info out there that either
posted a good recipe, or even said it was do-able. That said, the
qualities I'd like are: enough plasticity and strength for throwing up to
five pounds in a bottle or bowl shape (and not having to leave too much at
the base for support...I prefer to minimize my trimming). Translucency.
White-ness. Not having to fire in any kind of support structure, but not
having to worry about that puddle on the shelf if the kiln overfires by a
half-cone. Briefly, I'd like many of the qualities of a porcelain at cone
6...I just haven't found a prepared cone 6 body that I like so far. I have
my first experiments awaiting space in our next Cone 6 firing. Until I
know that the clay can handle it, I'm planning on 06 bisque before the
final high fire, tho' I may change to the traditional high bisque/low glaze
when/if I get a body I like. Of course, this may all be the thrill of the
hunt, and I will be "over it" once I finish experimenting. I'm still
mostly a cone 10 reduction stoneware guy. Cheers.
Snail Scott on sat 23 apr 05
Had an odd incident in grad school last week.
One of the other grad students is making a big=20
sculptural project out of many, many press-molded=20
pieces, all of bone china. They are thick (for bone=20
china) - up to 1-1/4" thick, but small - bloblike=20
chunks. They'd dried for quite a while, then been=20
candled overnight. She made 1400 of these little=20
things, so she was firing two kilnloads at once -=20
one electric and one gas.=20
Everything went smoothly until the kiln hit around=20
900=BAF. (Not precise, since the thermocouple wasn't=20
on that level.) All the pieces on the top shelf=20
exploded into smithereens, with puffs of the resulting=20
dust visible going up the chimney of the gas kiln.
The same thing happened to the load in the electric=20
kiln. (Possibly at the same temp, but not certain,=20
since it wasn't attended when the incident ocurred.)
There appeared to be faint signs of reduction on both=20
loads, including the electrically-fired work. About=20
150 pieces were destroyed, of several different=20
shapes made at different times.
I've never seen anything explode like that at such=20
a temperature. We've been speculating on what=20
may have happened, and right now the prevailing=20
notion (from Albert Pfarr) is that the bone ash=20
began to dissociate at that temperature, possibly=20
producing a lot of CO2.=20
Anyone ever experienced similar results with bone=20
china? Any ideas?
-Snail
Michael Wendt on sun 24 apr 05
Snail,
Between 500 and 800 degrees C, the water of hydration comes off. If the body
is fired too fast during that stage and is quite tight, it can also cause a
steam explosion.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave
Lewiston, Idaho 83501
USA
wendtpot@lewiston.com
www.wendtpottery.com
Snail wrote:
I've never seen anything explode like that at such
a temperature. We've been speculating on what
may have happened, and right now the prevailing
notion (from Albert Pfarr) is that the bone ash
began to dissociate at that temperature, possibly
producing a lot of CO2.
Anyone ever experienced similar results with bone
china? Any ideas?
-Snail
Debbie on sun 24 apr 05
Hi Snail,
I've experienced similar incidents with a variety of clays and given that
the exact temp of the occurrence is not know I speculated that moisture
could be the most likely cause.
A fine grained clay or one w/o grog, rather thick, even when candled over
night can still retain enough moisture to explode. (I've done a lot of force
drying and am always amazed how tenacious water in clay is. A piece removed
from a 4-500F or so degree kiln and placed on news papers will exude an
incredible amount of moister, you can see the effect on the paper. This even
after an overnight candling.) VIPs (very important pieces) now get a lot of
extra handling in a heat box or oven prior to firing and I live in a
relatively dry climate!
The irritating part is that the pyrometer says the kiln is well past the
danger area for steam, but it was taking more time for the pressure to reach
the exploding point. Time enough for the temp to get up to 400 to 800F
degrees, (in my case). Solved the problem by the above extra drying,
candling longer, giving a rest between two or more candle periods, jabbing
the backs or insides of thick parts with a needle tool about a half inch
apart. After these extra precautions I've not had any sculptures explode.
Best Wishes, Debbie in So CA
> -----Original Message-----
> From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Snail Scott
> Sent: Saturday, April 23, 2005 8:23 PM
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Bone China
>
>
> Had an odd incident in grad school last week.
> One of the other grad students is making a big
> sculptural project out of many, many press-molded
> pieces, all of bone china. They are thick (for bone
> china) - up to 1-1/4" thick, but small - bloblike
> chunks. They'd dried for quite a while, then been
> candled overnight. She made 1400 of these little
> things, so she was firing two kilnloads at once -
> one electric and one gas.
>
> Everything went smoothly until the kiln hit around
> 900ºF. (Not precise, since the thermocouple wasn't
> on that level.) All the pieces on the top shelf
> exploded into smithereens, with puffs of the resulting
> dust visible going up the chimney of the gas kiln.
> The same thing happened to the load in the electric
> kiln. (Possibly at the same temp, but not certain,
> since it wasn't attended when the incident ocurred.)
> There appeared to be faint signs of reduction on both
> loads, including the electrically-fired work. About
> 150 pieces were destroyed, of several different
> shapes made at different times.
>
> I've never seen anything explode like that at such
> a temperature. We've been speculating on what
> may have happened, and right now the prevailing
> notion (from Albert Pfarr) is that the bone ash
> began to dissociate at that temperature, possibly
> producing a lot of CO2.
>
> Anyone ever experienced similar results with bone
> china? Any ideas?
>>
Gary Harvey on mon 25 apr 05
I have no experience with bone china but I have had plenty of pottery
explode. It's caused by the pots not being completely dry. In other words
they were too wet to fire. Just a suggestion but you could leave the ware in
a heated room set to about 90 degrees for at least 2 weeks. Slow drying is
the key. I leave my pots on the kiln for the next firing. I also dry them
at least 5 days before that. In the summer here in Texas the time can be
cut shorter because it gets 100 here with 90 or more percent humidity. Good
luck, GH Palestine TX
----- Original Message -----
From: "Snail Scott"
To:
Sent: Saturday, April 23, 2005 10:23 PM
Subject: Bone China
Had an odd incident in grad school last week.
One of the other grad students is making a big
sculptural project out of many, many press-molded
pieces, all of bone china. They are thick (for bone
china) - up to 1-1/4" thick, but small - bloblike
chunks. They'd dried for quite a while, then been
candled overnight. She made 1400 of these little
things, so she was firing two kilnloads at once -
one electric and one gas.
Everything went smoothly until the kiln hit around
900ºF. (Not precise, since the thermocouple wasn't
on that level.) All the pieces on the top shelf
exploded into smithereens, with puffs of the resulting
dust visible going up the chimney of the gas kiln.
The same thing happened to the load in the electric
kiln. (Possibly at the same temp, but not certain,
since it wasn't attended when the incident ocurred.)
There appeared to be faint signs of reduction on both
loads, including the electrically-fired work. About
150 pieces were destroyed, of several different
shapes made at different times.
I've never seen anything explode like that at such
a temperature. We've been speculating on what
may have happened, and right now the prevailing
notion (from Albert Pfarr) is that the bone ash
began to dissociate at that temperature, possibly
producing a lot of CO2.
Anyone ever experienced similar results with bone
china? Any ideas?
-Snail
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Snail Scott on thu 28 apr 05
At 07:11 AM 4/24/2005 -0700, Michael W wrote:
>Snail,
>Between 500 and 800 degrees C, the water of hydration comes off. If the body
>is fired too fast during that stage and is quite tight, it can also cause a
>steam explosion...
I'm familiar with the theory; I just never saw it
happen before. That's one thing about sharing studio
space after years alone - you see things that your
own work habits would never produce! (Not that I'm
somehow superior and immune, but although I often
build quite thick, I've generally preferred very open
clay bodies.) You are most likely correct that it was
just a garden variety steam explosion, and since it
happened on the top shelves, it was probably heating
faster than the lower levels. I just wondered if there
was anything special about bone china (other than
being tight) which I'd never heard about, since I've
seldom used it.
The student replaced her missing parts, and with some
force-drying, her thesis show should go up next week
on schedule.
-Snail
James Freeman on thu 15 oct 09
On 10/14/09, Antoinette Badenhorst wrote:
> I wonder how long porcelain will still be a subject of dispute
> on this forum? What is it that keeps the subject so controversial? I wond=
er
> if it has anything to do with the very, very interesting history that lie=
s
> behind it.......or maybe because the clay is so tedious to work with ( oe=
ps,
> I got slapped for that in the past also, so I take that back )
>
One of my first posts on this list upon venturing out of lurkerdom was
in answer to someone's questions about porcelain dental crowns
(information came from my father, who was a dental technician). I was
told emphatically that dental porcelain is not porcelain, though it
say so on the jars and is fired to complete vitrification, because it
had too much feldspar and because you can't throw a pot with it.
...James
--
James Freeman
"All I say is by way of discourse, and nothing by way of advice. I
should not speak so boldly if it were my due to be believed."
-Michel de Montaigne
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/clayart/
piedpotterhamelin@COMCAST.NET on thu 15 oct 09
Hi everyone;=3D20
The revolutionary changes in the mid-18th century English ceramic whiteware=
=3D
industry were influenced by several fronts.=3D20
The earliest British whitebodies were made by John Dwight in 1640 are known=
=3D
as "white stoneware". These high temperature white wares were known as "fl=
=3D
int whiteware by the mid 18th c. and were followed in the first part of the=
=3D
18th century with earthenware cream colored "creamwares, queensware and pe=
=3D
arlware" the latter=3DC2=3DA0improved by Wedgwood on the whiteness by addin=
g a =3D
touch a cobalt as bluing. The use of china clay and china stone from Cornwa=
=3D
ll brought about these changes.=3D20
The porcelains were made as two types, Soft paste and Hard-paste, although =
=3D
one author stated that Bone China should be considered a third type, as a h=
=3D
ybrid because o f maturing temperature, but others include it their soft pa=
=3D
ste lists.=3D20
THE SOFT PASTES=3DC2=3DA0 include-=3D20
Glassy or=3DC2=3DA0fritted=3DC2=3DA0porcelain-dating to 16th c. Florence, c=
ontainin=3D
g powdered glass or frit. Manufactured later by Vincenne and Sevres. Too di=
=3D
fficult and unsuccessful for English potters.=3D20
Soapstone porcelain-steatite used a flux, ceramic vitrifies at a relatively=
=3D
low temperature. Withstands boiling water. Made by Bristol, Worcester, Liv=
=3D
erpool and Cauley in the 18th c.=3D20
STONEWARES=3D20
Ironstone china. Felspathic, Made by Mason, not a true bone china but a "wh=
=3D
ite stoneware". It is in dispute whether "ironstone' referred to the streng=
=3D
th of the ceramic or was made from the pudding=3DC2=3DA0+=3D20
-=3DC2=3DA0waste from processing iron ore.=3D20
HYBRID=3D20
Bone China-hybrid as neither a soft paste glassy porcelain or hard paste (a=
=3D
lthough some believe=3DC2=3DA0it=3DC2=3DA0to be hardpaste) =3DC2=3DA0as a f=
elspathic po=3D
rcelain; vitreous and translucent. High strength.=3DC2=3DA0 Originally was =
made=3D
with ox bones=3D20
Feldspar porcelain, feldspar china.=3DC2=3DA0=3DC2=3DA0A=3DC2=3DA0modified =
Bone China.=3D
=3DC2=3DA0Made by Spode, Coalport, Worcester and Derby. Cornish stone repla=
ced =3D
by feldspar (waste material from a=3DC2=3DA0welsh lead mine!) =3DC2=3DA0mix=
ed with =3D
ball clay, bone ash and sand frit. Great thermal properties, didn't crack l=
=3D
ike other soft pastes.=3D20
WHITEWARES=3D20
Stone China.=3DC2=3DA0 A combination of Tabberners mine rock with flint and=
Cor=3D
nish stone produced a white body called Turner's Patent. Spode later improv=
=3D
ed on the idea, buying the recipe from the bankrupted originators and creat=
=3D
ed Vitreous Whiteware. This was=3DC2=3DA0a plastic clay body comprised of b=
all =3D
clay, china clay, Cornish stone, flint, patent ironstone, perhaps a new nam=
=3D
e for the Tabberners rock. Superior to Mason's ironstone china.=3D20
=3DC2=3DA0=3D20
THE HARDPASTE=3D20
True porcelain, The standard is Chinese.=3D20
I hope you enjoyed this.=3D20
Rick=3D20
www.americanredware.com=3D20
Antoinette Badenhorst on thu 15 oct 09
Thanks for this information Rick. Senseful contribution to the subject.=3D2=
0
Antoinette Badenhorst=3D20
Lincolnshire, Illinoise=3D20
----- Original Message -----=3D20
From: piedpotterhamelin@COMCAST.NET=3D20
To: Clayart@LSV.CERAMICS.ORG=3D20
Sent: Thursday, October 15, 2009 7:42:26 AM GMT -06:00 US/Canada Central=3D=
20
Subject: Bone China=3D20
Hi everyone;=3D20
The revolutionary changes in the mid-18th century English ceramic whiteware=
=3D
industry were influenced by several fronts.=3D20
The earliest British whitebodies were made by John Dwight in 1640 are known=
=3D
as "white stoneware". These high temperature white wares were known as "fl=
=3D
int whiteware by the mid 18th c. and were followed in the first part of the=
=3D
18th century with earthenware cream colored "creamwares, queensware and pe=
=3D
arlware" the latter=3DC2=3DA0improved by Wedgwood on the whiteness by addin=
g a =3D
touch a cobalt as bluing. The use of china clay and china stone from Cornwa=
=3D
ll brought about these changes.=3D20
The porcelains were made as two types, Soft paste and Hard-paste, although =
=3D
one author stated that Bone China should be considered a third type, as a h=
=3D
ybrid because o f maturing temperature, but others include it their soft pa=
=3D
ste lists.=3D20
THE SOFT PASTES=3DC2=3DA0 include-=3D20
Glassy or=3DC2=3DA0fritted=3DC2=3DA0porcelain-dating to 16th c. Florence, c=
ontainin=3D
g powdered glass or frit. Manufactured later by Vincenne and Sevres. Too di=
=3D
fficult and unsuccessful for English potters.=3D20
Soapstone porcelain-steatite used a flux, ceramic vitrifies at a relatively=
=3D
low temperature. Withstands boiling water. Made by Bristol, Worcester, Liv=
=3D
erpool and Cauley in the 18th c.=3D20
STONEWARES=3D20
Ironstone china. Felspathic, Made by Mason, not a true bone china but a "wh=
=3D
ite stoneware". It is in dispute whether "ironstone' referred to the streng=
=3D
th of the ceramic or was made from the pudding=3DC2=3DA0+=3D20
-=3DC2=3DA0waste from processing iron ore.=3D20
HYBRID=3D20
Bone China-hybrid as neither a soft paste glassy porcelain or hard paste (a=
=3D
lthough some believe=3DC2=3DA0it=3DC2=3DA0to be hardpaste) =3DC2=3DA0as a f=
elspathic po=3D
rcelain; vitreous and translucent. High strength.=3DC2=3DA0 Originally was =
made=3D
with ox bones=3D20
Feldspar porcelain, feldspar china.=3DC2=3DA0=3DC2=3DA0A=3DC2=3DA0modified =
Bone China.=3D
=3DC2=3DA0Made by Spode, Coalport, Worcester and Derby. Cornish stone repla=
ced =3D
by feldspar (waste material from a=3DC2=3DA0welsh lead mine!) =3DC2=3DA0mix=
ed with =3D
ball clay, bone ash and sand frit. Great thermal properties, didn't crack l=
=3D
ike other soft pastes.=3D20
WHITEWARES=3D20
Stone China.=3DC2=3DA0 A combination of Tabberners mine rock with flint and=
Cor=3D
nish stone produced a white body called Turner's Patent. Spode later improv=
=3D
ed on the idea, buying the recipe from the bankrupted originators and creat=
=3D
ed Vitreous Whiteware. This was=3DC2=3DA0a plastic clay body comprised of b=
all =3D
clay, china clay, Cornish stone, flint, patent ironstone, perhaps a new nam=
=3D
e for the Tabberners rock. Superior to Mason's ironstone china.=3D20
=3DC2=3DA0=3D20
THE HARDPASTE=3D20
True porcelain, The standard is Chinese.=3D20
I hope you enjoyed this.=3D20
Rick=3D20
www.americanredware.com=3D20
Antoinette Badenhorst on thu 15 oct 09
David B umee wrote:=3D20
It is incorrect to call bone china porcelain. Bone china is bisque fired to=
=3D
a high temperature, about cone 8, and glaze fired to a lower temperature, =
=3D
about cone 1. Porcelain derives from the process of glaze and clay maturing=
=3D
together at cone 9 and above, in some cases up to cone 13. At these temper=
=3D
atures, depending on the make-up of the body, an interface is created betwe=
=3D
en clay and glaze so that there is no distinct line between where the glaze=
=3D
ends and the clay begins. This gives porcelain an important strength and r=
=3D
esilience to knife marks that cannot be present with bone china.=3D20
David here we go again: What is porcelain and what not! Please read my answ=
=3D
er correctly: I call it a TYPE of porcelain.. The term "porcelain" is the o=
=3D
verall collective word for Soft paste porcelain, Hardpaste porcelain and Bo=
=3D
ne china. I did not call bone china=3DC2=3DA0 " Hard paste porcelain"=3DC2=
=3DA0 You=3D
r description is correct for hard paste porcelain. Your description for the=
=3D
firing temperatures of bone china is also correct, but the mistake that yo=
=3D
u make is that you do not distinct between the 2(or 3)=3DC2=3DA0types of po=
rcel=3D
ain.=3D20
Here are a few references:=3D20
Susan Peterson - Craft and Art of Clay: page 141=3D20
Peter Lane - Studio=3DC2=3DA0 porcelain : page 18 &19=3D20
In Contemporary Porcelain ( page 17) , Peter Lane=3DC2=3DA0 explains what h=
appe=3D
ns=3DC2=3DA0 when bleaching yellow ferric iron from porclain in the reducti=
on p=3D
rocess.................he goes on to say that a similar process takes place=
=3D
in bone china where the phosphate in bone ash in effect bleaches the iron.=
=3D
The res ult=3DC2=3DA0 is an almost pure white body that is translucent . T=
he a=3D
mount of bone ash needed to ensure=3DC2=3DA0 for all the iron to combine wi=
th t=3D
he phosphate is very high and end up taking plasticity out.=3DC2=3DA0 he we=
nt o=3D
n to say that it can be described as a PORCELAIN body, mixed equaly with bo=
=3D
ne ash. There is much more in this book about bone china.=3D20
Hamer and Hammer describes it as follows: =3DC2=3DA0" A British porcelain..=
....=3D
.... page 31. The clay is fired to translucent phase without glaze, then gl=
=3D
azed and fired at a low temperature.... a typical recipe for bone china: ch=
=3D
ina clay 25, feldspar 25 and bone ash 50=3D20
http://en.wikipedia.org/wiki/Porcelain=3D20
Okay: I rest my case, right there.I have much more examples from many more=
=3D
=3DC2=3DA0books.=3DC2=3DA0I wonder how long porcelain will still be a subje=
ct of di=3D
spute on this forum? What is it that keeps the subject so controversial? I =
=3D
wonder if it has anything to do with the very, very interesting history tha=
=3D
t lies behind it.......or maybe because the clay is so tedious to work with=
=3D
( oeps, I got slapped for that in the past also, so I take that back )=
=3D
=3D20
Antoinette Badenhorst=3D20
Lincolnshire, Illinoise=3D20
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