laffnbearclay on thu 4 aug 05
Thank you Paul Lewing.
Karin
----- Original Message -----=20
From: Paul Lewing=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Thursday, August 04, 2005 6:35 PM
Subject: Re: Arsenic in glazes?
on 8/4/05 12:34 PM, laffnbearclay at laffnbearclay@NPGCABLE.COM wrote:
> I'm showing my ignorance here, what outside of lead makes yellows =
and =3D
> reds etc? Isn't arsenic used in paints (canvas)?
Lead arsenate was the first opacifier used in ceramics, and it, along =
with
Purple of Cassius gold color, was the basis for the switch from =
famille
verte to famille rose colors is overglaze enamels in the early 18th =
century.
By mid-19th century its use had been pretty much superceded by tin =
oxide,
and later by zirconium. It is never used in glazes or ceramic =
enamels
today.
Other elements that may make yellow -, under certain conditions, in =
ceramics
are antimony, cadmium, praseodymium, chrome, titanium, iron, and
vanadium/tin.
You can make some shade of red out of cadmium, iron, chrome/tin or =
gold.
>
> If I am making a fool out of myself, I apologize in advance and will =
=3D
> wipe the egg off my face.
We'd think you more of a fool if you hadn't asked.
Paul Lewing, Seattle
=
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laffnbearclay on thu 4 aug 05
I'm showing my ignorance here, what outside of lead makes yellows and =
reds etc? Isn't arsenic used in paints (canvas)?
If I am making a fool out of myself, I apologize in advance and will =
wipe the egg off my face.
Karin Hurt
www.Laughingbearpottery.com
Paul Lewing on thu 4 aug 05
on 8/4/05 12:34 PM, laffnbearclay at laffnbearclay@NPGCABLE.COM wrote:
> I'm showing my ignorance here, what outside of lead makes yellows and =
> reds etc? Isn't arsenic used in paints (canvas)?
Lead arsenate was the first opacifier used in ceramics, and it, along with
Purple of Cassius gold color, was the basis for the switch from famille
verte to famille rose colors is overglaze enamels in the early 18th century.
By mid-19th century its use had been pretty much superceded by tin oxide,
and later by zirconium. It is never used in glazes or ceramic enamels
today.
Other elements that may make yellow -, under certain conditions, in ceramics
are antimony, cadmium, praseodymium, chrome, titanium, iron, and
vanadium/tin.
You can make some shade of red out of cadmium, iron, chrome/tin or gold.
>
> If I am making a fool out of myself, I apologize in advance and will =
> wipe the egg off my face.
We'd think you more of a fool if you hadn't asked.
Paul Lewing, Seattle
Snail Scott on fri 5 aug 05
At 12:34 PM 8/4/2005 -0700, you wrote:
>I'm showing my ignorance here, what outside of lead makes yellows and reds
etc?
Mostly cadmium, which is also a low-temperature
colorant, and tends to burn out above earthenware
temperatures. This is why you seldom see such colors
in stoneware. There are new-fangled stains which
encapsulate the cadmium in a zirconium shell to
protect it, and I'm told they work well at high
temperatures, though I don't use them myself.
Uranium was formerly used, but not anymore. You may
encounter examples in antiques shops, though.
Reds can be achieved with copper, in a reduction
atmosphere.
I've never heard of arsenic-based glaze colorants,
even at earthenware temperatures. Possibly they
were used historically, but I'd have to check.
Anyhow, you won't encounter them in current use.
-Snail
Edouard Bastarache Inc. on fri 5 aug 05
Hello all,
the works on Cadmium by Smart.Conseil of the Gien Factory (France)
Later,
"Ils sont fous ces quebecois"
"They are insane these quebekers"
"Están locos estos quebequeses"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://retrodemonstration.blogspot.com/
http://www.flickr.com/photos/potier/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Edouard Bastarache Inc. on fri 5 aug 05
Ooops,
here is the URL
http://perso.wanadoo.fr/smart2000/Cadmium.htm#english%20legis
"Ils sont fous ces quebecois"
"They are insane these quebekers"
"Están locos estos quebequeses"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://retrodemonstration.blogspot.com/
http://www.flickr.com/photos/potier/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Rick Hamelin on fri 5 aug 05
I hope this makes it to ClayArt. It seems that a majority of my posts never do. Most recently, my reply about the cowhorn sliptrailers didn't make it. If this one does...
Well, arsenic was used at least in the late eighteenth and nineteenth centuries for yellow. In the 1950's it was uranium that gave the red and oranges. Fiestaware and franciscanware were actually recalled by the Reagan Administration for the radioactivity.
Rick
If anyone can tell me why my replies don't get posted some of the time, just let me know. I don't include the original post, just the subject
--
"Many a wiser men than I hath
gone to pot." 1649
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