gwyna on thu 14 aug 03
I undertook research into writings and reports on Lead Glazes from many =
sources..a few years ago. Lead Bisilicate is recorded as being very =
stable and giving little or no Lead release from the finished =
pot........ provided no substance was added which would affect this =
stability. Avoid ....Copper,cadmium,Barium,Cobalt,Borax or Boric =
Acid,Zinc,Soda Ash,Nickel,Colemanite and other natural =
Borates,NaturalBoneAsh,Potash,Chromium,Selenium,Manganese,
Lithium,or any salts or compounds of any of these substances.
Any of these when used in..on..or under the glaze may reduce stability =
to some degree.Do not ballmill the frit.
Most natural clays MAY contain a soluble content which should be =
avoided for maximum safety and should be well washed.
BUT I would never advocate the use of any Lead Glaze in an educational =
environment.
All glazes should be on a mature body.. absorption less the 10% ..Matt =
or immature surfaces should not be used.
These are just some of my findings
Good Potting GWYN in N.Z.
Ron Roy on fri 15 aug 03
First of all my idea of a mature body would be one that did not leak - that
means the absorbency should be under about 3%
By the way - lead frits - OK lets say many frits - no lets say the
majority of frits are not what would prove out to be stable glazes. In
other words - they can be attacked by acids - and whatever is in them is
released.
Remember the cautions about not eating in the glaze room - that means -
when some of the materials we use get into you stomach and lungs - they can
be dissolved and whatever is in them gets in you.
My point is - to make a stable glaze out of any kind of lead - including
lead frits takes skill. The only way you know if you have succeeded is by
having the glaze tested.
There is no room in the class room for lead glazes - I would be surprised
if it was not against the law.
RR
>All glazes should be on a mature body.. absorption less the 10% ..Matt or
>immature surfaces should not be used.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
