Dov Katz on tue 22 jun 99
I've recently come across a small amount of lead chromate in a box of
hand-me-down glaze ingredients. Anyone have any glaze ideas for this stuff?
I've only got about a 1/4 lb. and can't really make a lot of test batches.
Sounds toxic in any case...I'll take the usual safety precautions.
Thanks in advance.
Dov Katz
Victoria, BC
Canada
Louis H.. Katz on thu 24 jun 99
There are some Beautiful Chrome lead oranges and reds at around 010
Here is one that I believe Gail Busch , my wife used about ten years ago.
Unfortunately it does not include Lead chromate but would need recalculation. I
don't have a formula for lead chromate at home.
Glaze name: Chrome Red Gloss
Cone: 010
Color: red
Surface texture: Shiny or Glossy
Firing: Ox.
Red Lead 80.39
Potash Spar 10.78
Barium Carbonate 3.92
Flint 4.91
Totals: 100.00
Also add:
Chromium Oxide 5.80
Unity Formula for Chrome Red Gloss:
0.316 K2O] 0.474 Al2O3 5.395 SiO2]
0.132 Na2O 11.4:1 Si:Al Ratio
0.026 CaO?
0.526 BaO?
Percentage Analysis:
65.80 % SiO2
9.81 % Al2O3
6.05 % K2O
1.67 % Na2O
0.30 % CaO
16.39 % BaO
Dov Katz wrote:
> ----------------------------Original message----------------------------
> I've recently come across a small amount of lead chromate in a box of
> hand-me-down glaze ingredients. Anyone have any glaze ideas for this stuff?
> I've only got about a 1/4 lb. and can't really make a lot of test batches.
> Sounds toxic in any case...I'll take the usual safety precautions.
>
> Thanks in advance.
> Dov Katz
> Victoria, BC
> Canada
--
Louis Katz
Michael Banks on fri 25 jun 99
Lead Chromate should be a good starting material for scarlet red
low-temperature glazes. In nature lead chromate exists as the mineral
crocoite (PbCrO4). Very striking monoclinic brilliant-red to orange
prismatic crystals of crocoite are keenly sought by collecters. Crocoite
has a low tolerance to heating, decomposing below 1000 degrees to lead oxide
and green chromic oxide.
This explains why lead-chromium red glazes are best fired below orton cone
06. The brilliant reds, oranges, vermillion and yellow colours achieved in
these glazes is due to precipitation of crocoite crystals. The glaze is
oversaturated in the lead chromate components and therefore combining raw
lead chromate with an appropriate low alumina flux to mature about 900
degrees C, should result in some good reds to yellows.
Lead chromate is toxic and regarded as teratogenic, mutagenic and
carcinogenic. The same goes for glazes saturated in lead and chrome, take
care.
Michael Banks,
Nelson
New Zealand
Empiricism is the antidote to ideology
> ----------------------------Original message----------------------------
> I've recently come across a small amount of lead chromate in a box of
> hand-me-down glaze ingredients. Anyone have any glaze ideas for this
stuff?
> I've only got about a 1/4 lb. and can't really make a lot of test batches.
> Sounds toxic in any case...I'll take the usual safety precautions.
>
> Thanks in advance.
> Dov Katz
> Victoria, BC
> Canada
| |
|
