iandol on tue 2 apr 02
Dear Gwyn Ace,
Most certainly Lead, in some form or another, will evaporate from the =
surface of a pot fired with a lead glaze. If the atmosphere is reducing =
then it may be elemental lead which is discharged.
But the definitive tests for this are Weight Difference, not a change in =
surface texture, and some form of material analysis.
Multiple firings and coolings can lead to segregation and =
crystallisation which change the surface texture. Other fluxing agents =
can also flash nearby hot clay. We know very little about these glaze =
chemistries
I wholeheartedly agree with you. Pot in safety.
Best regards,
Ivor.
Paul Lewing on wed 3 apr 02
on 4/3/02 3:17 PM, Edouard Bastarache at edouardb@SOREL-TRACY.QC.CA wrote:
> Basic lead carbonate (C2H2O8Pb3) is unstable under the following conditions
> : if heated it decomposes at 400 C and emits lead monoxide, carbon monoxide
> and carbon dioxide.
>
> Red lead (Pb3O4)) is unstable under the following conditions : if heated to
> decomposition (over 500 C), there is release of oxygen and emission of toxic
> fumes of lead.
>
> Yellow lead ((Pb) is unstable under the following conditions: if heated at
> 300-400 C
> it transforms into lead tetraoxide.
Edouard, does lead bisilicate also decompose? If so, under what conditions
and with what byproducts?
Paul Lewing, Seattle
Edouard Bastarache on wed 3 apr 02
Hello Ivor,
Basic lead carbonate (C2H2O8Pb3) is unstable under the following conditions
: if heated it decomposes at 400 C and emits lead monoxide, carbon monoxide
and carbon dioxide.
Red lead (Pb3O4)) is unstable under the following conditions : if heated to
decomposition (over 500 C), there is release of oxygen and emission of toxic
fumes of lead.
Yellow lead ((Pb) is unstable under the following conditions: if heated at
300-400 C
it transforms into lead tetraoxide.
Later,
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
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