Steve Slatin on wed 14 oct 09
Lead crystal isn't actually the same as
other glasses. It has different optical
characteristics because it's a denser
material, and has a higher index of
refraction; that's why it has the sparkle.
The ringing from lead glass is also
related to the the different characteristics;
though some early glass has been found
with small concentrations of lead that
indicate that it may have been used as
an additional melting agent.
Steve Slatin --
--- On Wed, 10/14/09, Ann Brink wrote:
> Regarding lead crystal, I don't think
> the addition of lead was only for
> fluxing- just as a clear glaze containing lead has a super
> shiny look, lead
> crystal has that extra sparkle, IMO.
>
> Ann Brink in Lompoc CA
mel jacobson on wed 14 oct 09
what is bone china?
i assume it the addition of calcium in the form
of bone ash. it was a simple additive to give the
porcelain a bit of strength. ??? is that correct?
or, was it just a filler, and an ad campaign to make
it seem wonderful.
same for `LEAD CRYSTAL`. it was a big deal years back, as
if they added a magic ingredient.
obviously it was a glass flux, and lowered the melting point
a bit, save money on fuel.
but then.
?
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
Lee Love on wed 14 oct 09
On Wed, Oct 14, 2009 at 1:01 PM, mel jacobson wrote:
> what is bone china?
>
> i assume it the addition of calcium in the form
> of bone ash. =3DA0it was a simple additive to give the
> porcelain a bit of strength. =3DA0??? is that correct?
"Found" in the translation. From the Wiki:
Bone china
It has been suggested that a misunderstanding of an account of
porcelain manufacture in China given by a Jesuit missionary was
responsible for the first attempts to use bone-ash as an ingredient of
Western porcelain (in China, china clay was sometimes described as
forming the bones of the paste, while the flesh was provided by
refined porcelain stone)[citation needed]. For whatever reason, when
it was first tried it was found that adding bone-ash to the paste
produced a white, strong, translucent porcelain. Traditionally English
bone china was made from two parts of bone-ash, one part of china clay
kaolin and one part china stone (a feldspathic rock), although this
has largely been replaced by feldspars from non-UK sources.[3]
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Ann Brink on wed 14 oct 09
Regarding lead crystal, I don't think the addition of lead was only for
fluxing- just as a clear glaze containing lead has a super shiny look, lead
crystal has that extra sparkle, IMO.
Ann Brink in Lompoc CA
(mostly about pottery)
----- Original Message -----
From: "mel jacobson"
> what is bone china?
>
> i assume it the addition of calcium in the form
> of bone ash. it was a simple additive to give the
> porcelain a bit of strength. ??? is that correct?
>
> or, was it just a filler, and an ad campaign to make
> it seem wonderful.
>
> same for `LEAD CRYSTAL`. it was a big deal years back, as
> if they added a magic ingredient.
> obviously it was a glass flux, and lowered the melting point
> a bit, save money on fuel.
> but then.
> ?
> mel
> from: minnetonka, mn
> website: http://www.visi.com/~melpots/
> clayart link: http://www.visi.com/~melpots/clayart.html
> new book: http://www.21stcenturykilns.com
---------------------------------------------------------------------------=
-----
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06:33:00
Antoinette Badenhorst on wed 14 oct 09
Mel, bone china is a type of porcelain that contains all or most of porcela=
=3D
in ingredients, but with bone ash added - up to 50 %. Bone ash is a calcium=
=3D
phosphate, a flux that brings the temperature tolerance of bone china down=
=3D
to I think ...almost earhernware temps. Few potters work with it. Sasha Wa=
=3D
rdell is probably the most known today. It is not a plastic claybody and mo=
=3D
st studio potters that work with it cast their ware. Beautiful, and very tr=
=3D
anslucent. Mostly used in industry.=3D20
=3DC2=3DA0Martha Zettler is a potters friend of mine working in this medium=
. He=3D
re is her website: http://marthazettler.com/=3D20
what is bone china?=3D20
i assume it the addition of calcium in the form=3D20
of bone ash. it was a simple additive to give the=3D20
porcelain a bit of strength. ??? is that correct?=3D20
or, was it just a filler, and an ad campaign to make=3D20
it seem wonderful.=3D20
same for `LEAD CRYSTAL`. it was a big deal years back, as=3D20
if they added a magic ingredient.=3D20
obviously it was a glass flux, and lowered the melting point=3D20
a bit, save money on fuel.=3D20
but then.=3D20
Antoinette Badenhorst=3D20
Lincolnshire, Illinoise=3D20
Earl Krueger on wed 14 oct 09
Mel,
What I know:
The lead in crystal increases the index-of-refraction
of the glass making it bend light more making it
sparkle more and produce coloured (rainbow) effects.
What I think I know:
Bone ash in porcelain adds phosphorous to the mix
which adds another glass maker which makes the
porcelain more translucent.
Or, at least that's what I think I remember reading.
Earl Krueger
Oregon, USA
douglas fur on wed 14 oct 09
On Wed, Oct 14, 2009 at 11:01 AM, mel jacobson wrote: what is bone china?
i assume it the addition of calcium in the form of bone ash.
was it a simple additive to give the porcelain a bit of strength. ???
The Calcium lowered the firing temp from1300c to 1200c, easier for the
English technology to reach.
The phosphorus turned out to add strength
ad campaign- I have an english pottery (*The Potters Manual* Kenneth Clarke
?) that claims 4 teacups were used to support a London bus in a promo event
DRB
Seattle
douglas fur on wed 14 oct 09
, Antoinette Badenhorst
"Few potters work with it."
I've been testing it as a body for mid range firing but not for translucent
whiteware.
I've tried adding it in the range of !/12th to 1/7th
So far body colors seem warmer.
DRB
Seattle
http://marthazettler.com/
claybuds@ATT.NET on wed 14 oct 09
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 Beumee
Lafayette, CO
=3DC2=3DA0 -------------- Original message from Antoinette Badenhorst yart=3D
_friends10@COMCAST.NET>: --------------=3D20
Mel, bone china is a type of porcelain that contains all or most of porcel=
=3D
ain ingredients, but with bone ash added - up to 50 %. Bone ash is a calci=
=3D
um phosphate, a flux that brings the temperature tolerance of bone china d=
=3D
own to I think ...almost earhernware temps. Few potters work with it. Sash=
=3D
a Wardell is probably the most known today. It is not a plastic claybody a=
=3D
nd most studio potters that work with it cast their ware. Beautiful, and v=
=3D
ery translucent.=3D20=3D20
> Mostly used in industry.=3D20=3D20
> =3DC2=3DA0Martha Zettler is a potters friend of mine working in this med=
ium.=3D
Here is her=3D20=3D20
> website: http://marthazettler.com/=3D20=3D20
>=3D20=3D20
>=3D20=3D20
>=3D20=3D20
>=3D20=3D20
>=3D20=3D20
> what is bone china?=3D20=3D20
>=3D20=3D20
> i assume it the addition of calcium in the form=3D20=3D20
>=3D20=3D20
> of bone ash. it was a simple additive to give the=3D20=3D20
>=3D20=3D20
> porcelain a bit of strength. ??? is that correct?=3D20=3D20
>=3D20=3D20
> or, was it just a filler, and an ad campaign to make=3D20=3D20
>=3D20=3D20
> it seem wonderful.=3D20=3D20
>=3D20=3D20
> same for `LEAD CRYSTAL`. it was a big deal years back, as=3D20=3D20
>=3D20=3D20
> if they added a magic ingredient.=3D20=3D20
>=3D20=3D20
> obviously it was a glass flux, and lowered the melting point=3D20=3D20
>=3D20=3D20
> a bit, save money on fuel.=3D20=3D20
>=3D20=3D20
> but then.=3D20=3D20
>=3D20=3D20
> Antoinette Badenhorst=3D20=3D20
> Lincolnshire, Illinoise=3D20=3D20=3D20
William & Susan Schran User on wed 14 oct 09
On 10/14/09 2:01 PM, "mel jacobson" wrote:
> what is bone china?
>
> i assume it the addition of calcium in the form
> of bone ash. it was a simple additive to give the
> porcelain a bit of strength. ??? is that correct?
I recall reading that adding bone ash to a white clay/porcelain like clay
was to lower the fusion/vitrification temperature of the clay to produce a
product similar to porcelain produced in China, but done in Europe at lower
temperatures.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
steve graber on wed 14 oct 09
nice question, i thought bone china was simply a name for "whitish=3D
=3D0A=3D0A=3D0Anice question, i thought bone china was simply a name for "w=
hitish=3D
" clay.=3DA0 as a kid before i was into clay that was the distinction my fa=
mi=3D
ly made for the "white stuff" vs the stoneware toasty colors.=3DA0 =3D0A=3D=
0Aalso=3D
, i swear the leaded crystal was a marketing=3DA0ploy.=3DA0 again as a kid =
my p=3D
arents thought "ooooh!=3DA0 leaded crystal!"=3DA0 they didn't know good stu=
ff f=3D
rom bad stuff so if someone labled something as "leaded crystal" the value =
=3D
went up in their minds.=3DA0=3DA0lead might have been more-needed from a gl=
ass =3D
blowing point of view than the manufactured glass?=3DA0 =3D0A=3D0A=3D0A=3D0=
A=3DA0Steve =3D
Graber, Graber's Pottery, Inc=3D0AClaremont, California USA=3D0AThe Steve T=
ool =3D
- for awesome texture on pots! =3D0Awww.graberspottery.com steve@graberspot=
te=3D
ry.com =3D0A=3D0A=3D0AOn Laguna Clay's website=3D0Ahttp://www.lagunaclay.co=
m/blogs/=3D
=3D0A=3D0A=3D0A=3D0A=3D0A________________________________=3D0AFrom: mel ja=
cobson ots2@VISI.COM>=3D0ATo: Clayart@LSV.CERAMICS.ORG=3D0ASent: Wed, October 14, =
2009=3D
11:01:18 AM=3D0ASubject: bone china/question=3D0A=3D0Awhat is bone china?=
=3D0A=3D0Ai=3D
assume it the addition of calcium in the form=3D0Aof bone ash.=3DA0 it was=
a s=3D
imple additive to give the=3D0Aporcelain a bit of strength.=3DA0 ??? is tha=
t co=3D
rrect?=3D0A=3D0Aor, was it just a filler, and an ad campaign to make=3D0Ait=
seem =3D
wonderful.=3D0A=3D0Asame for `LEAD CRYSTAL`.=3DA0 it was a big deal years b=
ack, a=3D
s=3D0Aif they added a magic ingredient.=3D0Aobviously it was a glass flux, =
and =3D
lowered the melting point=3D0Aa bit, save money on fuel.=3D0Abut then.=3D0A=
?=3D0Ame=3D
l=3D0Afrom: minnetonka, mn=3D0Awebsite: http://www.visi.com/~melpots/=3D0Ac=
layart=3D
link:=3DA0 http://www.visi.com/~melpots/clayart.html=3D0Anew book: http://=
www.=3D
21stcenturykilns.com=3D0A=3D0A=3D0A________________________________________=
______=3D
____=3D0ADo You Yahoo!?=3D0ATired of spam? Yahoo! Mail has the best spam p=
rote=3D
ction around =3D0Ahttp://mail.yahoo.com
Paul Lewing on wed 14 oct 09
On Oct 14, 2009, at 11:01 AM, mel jacobson wrote:
what is bone china?
Here's an interesting story, perhaps apocryphal, just in case you ever
wondered how they ever came up with the idea of putting burned cattle
bones into their clay.
Before everyone in Europe had figured out how to make porcelain,
potters were trying everything they could think of and looking for any
source of information they could find. A French Jesuit missionary
named Pere D'Entrecolles had been in Jingdezhen and been inside the
porcelain factories. He knew nothing about what he was looking at,
but he wrote two letters home, in 1712 and 1722, describing as best he
could what was going on and reporting on what people told him. The
story goes that a Chinese potter had told him that making porcelain
without kaolin was like making a body without bones. English potters
read this (translated from Chinese to French to English of course, so
who knows what was actually said) and went, "Hmmmmm....... bones, you
say".
Paul Lewing
www.paullewingtile.com
www.paullewingart.com
marci and rex on wed 14 oct 09
At 03:54 PM 10/14/2009, douglas fur wrote:
>ad campaign- I have an english pottery (*The Potters Manual* Kenneth Clark=
e
>?) that claims 4 teacups were used to support a London bus in a promo even=
t
It happened several times with cars :
A Rolls was set on 4 Wedgewood teacups
: http://articles.latimes.com/1985-11-11/news/mn-4010_1
Wm Ashley China did it with
a Tesla roadster
http://www.madwhips.com/tesla-roadster-on-teacups-in-toronto/
and
http://green.autoblog.com/2009/09/12/tesla-roadster-on-four-teacups-plus-jo=
nas-brothers/
marci
www.ppio.com
Des & Jan Howard on thu 15 oct 09
David
I feel you are giving a shallow Europo-centric view on
what constitutes porcelain. Check out development of
Northern Chinese porcelain ware. Nigel Wood is a good
source.
Des
claybuds@ATT.NET wrote:
> It is incorrect to call bone china porcelain.
Bone china is bisque fired to a high temperature,
about cone 8, and glaze fired to a lower temperature,
about cone 1. Porcelain derives from the process
of glaze and clay maturing together at cone 9 and above,
in some cases up to cone 13. At these temperatures,
depending on the make-up of the body, an interface
is created between clay and glaze so that there is
no distinct line between where the glaze ends and
the clay begins. This gives porcelain an important
strength and resilience to knife marks that cannot
be present with bone china.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
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