"Rafael Molina-Rodriguez (Rafael Molina-Rodriguez)" on tue 3 jun 97
Talbot :
>I was wondering if chromium could produce yellow under certain >conditions
In fact, it does. A small amount of chrome oxide ( .5 % to 1 %) will
produce yellow in a lead or lead bisilicate base at ^ 03. Too much yellow
and it will be chartreuse green.
I've experimented with a lead bisilicate base out of "The Potter's Palette."
IMHO, really some of the most beautiful transparent copper greens, cobalt
blues, red iron ambers, and chrome yellows I've achieved on a white
earthenware or red terra cotta claybody. It's my understanding that lead
bisilicate, while still hazardous, is not as hazardous as lead oxide (white
or red). My information on this subject comes from Susan Peterson in her
book the Craft and Art of Clay." She states :
"The danger of lead may be overrated, but it is controversial and
currently the subject of legal discussion in the United States that
may totally ban its use in ceramics as well as in other fields. Lead
is one of the most active fluxes, especially at low temperature, and
influences color in ways that no other known material
does; it is in
fact irreplaceable. Raw lead compunds such as lead oxide, white
lead, and galena are soluble and possibly poisonous (if ingested)
until fired above 2000 F. The process of fitting complex lead-bearing
compositions, or simple frits lead mono- and bisilicate, renders the
poisonous ingrediants insoluble and non-poisonous."
As I said, I've only experimented with this glaze on test tiles. If I ever
use on actual work I'll only use on surfaces which will not come in contact
with food.
Any thoughts from the group about Peterson's ideas about lead?
Rafael
rmr3431@dcccd.edu
Ron Roy on wed 4 jun 97
> Susan Peterson in her book the Craft and Art of Clay." states :
> Raw lead compunds such as lead oxide, white
> lead, and galena are soluble and possibly poisonous (if ingested)
> until fired above 2000 F. The process of fitting complex lead-bearing
> compositions, or simple frits lead mono- and bisilicate, renders the
> poisonous ingrediants insoluble and non-poisonous."
>Any thoughts from the group about Peterson's ideas about lead?
Hi Rafael,
It's not often possible in this business to comment without some sort of
qualification. In this case it's plain to see - she does not know what she
is talking about.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/ronroy.htm
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