John Hesselberth on wed 14 nov 01
on 11/14/01 11:33 AM, Lesley Alexander at celadon@SILCOM.COM wrote:
> Received test results from Alfred=92s lab. They included drinking water
> standards provided by EPA with each result, except for cobalt, which has
> no standard. It can be argued whether or not we have to meet those water
> standards in a leach test, and that=92s one I can=92t answer. However, for
> liner glazes I=92ll mostly stick to whites and glazes with only moderate
> additions of rutile or iron oxide for liner glazes.
> The result for the Oribe surprised me=85 I would have thought 6.5%
> copper carb would be excessive. And the results for cobalt I can=92t
> interpret at all. Can anyone help here? Best wishes, Lesley
Hi Leslie,
Thanks for sharing your results! The cobalt numbers look like they are
really low and way toward the stable end of the spectrum. I wouldn't be
concerned about them.
I am puzzled by the copper numbers, though, to the extent I'm going to make
some inquiries at Alfred Analytical and see if something has changed. The
Oribe glaze is not a particularly good glaze with respect to its alumina an=
d
silica levels. I just don't think there is any way the number they reporte=
d
can be correct. The glaze you call K. Baker Oribe is identical to Shaner's
Oribe which Tom Wirt and Betsy Price had tested a couple years ago. They
got 52.5 mg/l Cu--that is over 150 times what you got and, frankly, is
closer to what I would expect from that glaze.
I have a similar problem believing the results on Toni's copper. While it
is a much better glaze from the standpoint of silica and alumina. Glazes
with 4% copper carbonate just don't leach that little amount. I would have
expected 1-2 mg/l instead of 0.03
I haven't looked closely at the others--copper always catches my attention
first because I've tested so many copper-containing glazes and I know what
to expect.
I'll let you know if I learn anything from Alfred Analytical, but this
raises serious concerns with me.
Regards,
John
Web site: http://www.frogpondpottery.com Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Lesley Alexander on wed 14 nov 01
Received test results from Alfred’s lab. They included drinking water
standards provided by EPA with each result, except for cobalt, which has
no standard. It can be argued whether or not we have to meet those water
standards in a leach test, and that’s one I can’t answer. However, for
liner glazes I’ll mostly stick to whites and glazes with only moderate
additions of rutile or iron oxide for liner glazes.
The result for the Oribe surprised me… I would have thought 6.5%
copper carb would be excessive. And the results for cobalt I can’t
interpret at all. Can anyone help here? Best wishes, Lesley
A. White Waxy + De Gussa
Laguna’s White Waxy 100
De Gussa yellow (enclosed cadmium) 3.0%
Chrome .5%
Blushing Clear with Nile Turquoise
RESULTS: Cadmium <.002 mg/L
Chromium <.004 mg/L
B. Toni’s copper
======================
Feldspar 40.00
EPK 10.00
Whiting 20.00
Silica 30.00
========
100.00
Add 4% cu carb
RESULTS: Copper .03 mg/L
C. Emily’s Purple
41.00 Potash Feldspar
12.00 Colemanite
7.00 Dolomite
15.00 Talc
5.00 Tennessee #5 Ball Clay
20.00 Silica
100.00 % Totals:
Also add:
2.00 Cobalt Oxide
2.00 Bentonite
2.00 Tin Oxide
RESULTS: COBALT .03
D. Strontium chun blue
Custer 48.8
EPK 1.5
Gerstley Borate 9.1
Dolomite 9.1
Whiting 2.7
Strontium 4.6
Zinc 1.8
Zircopax .6
Cobalt Carb .5
Rutile 5.2
RESULTS: Cobalt <.002 mg/L
Toni’s and Blue Ice
(Toni’s Copper over AE Blue Ice)
F. AE Blue Green
Laguna MG2 or White Waxy
Chrome
Cobalt
G. Delft Blue
Custer Spar 26.96
Whiting 19.20
EPK 19.60
Silica 32.24
Add Cobalt 250 (2.5%)
RESULTS: Cobalt .004
H. Red Glaze:
Basic clear glaze (CB, Vivika’s) + 4% de gussa light red
======================
(Partly Vivika Heino’s base glaze:
Custer Spar 27.48
EPK 19.95
Dolomite 19.57
Silica 32.94
And partly Carlton Ball clear:
Feldspar 250
EPK 200
Whiting 250
Silica 300
Plus 4% De Gussa light red
RESULTS: Cadmium .003 mg/L
I. AE Chun Blue
J. Long Beach Blue
Feldspar 63.55
Whiting 19.49
EPK 16.96
Cobalt 85
Rutile 400
RESULTS: Cobalt .004 mg/L
K. Baker Oribe
Oribe Cone 9-10 (BG ORIBE)
Bone ash 1.1
Talc 7.8
Whiting 22.4
Potash Feldspar 30.9
EPK kaolin 12.5
flint 25.3
+copper carbonate 5.5%
RESULTS: Copper .3
For email:
Received test results from Alfred’s lab. They included drinking water
standards provided by EPA with each result, except for cobalt, which has
no standard. It can be argued whether or not we have to meet drinking
water standards in a leach test, and that’s one I can’t answer.
However, I’ll stick to whites and glazes with only moderate additions of
rutile or iron oxide for liner glazes.
A. White Waxy + De Gussa
Laguna’s White Waxy 100
De Gussa yellow (enclosed cadmium) 3.0%
Chrome .5%
Blushing Clear with Nile Turquoise
RESULTS: Cadmium <.002 mg/L; later, ..005
Chromium <.004 mg/L; later, .05
B. Toni’s copper
======================
Feldspar 40.00
EPK 10.00
Whiting 20.00
Silica 30.00
========
100.00
Add 4% cu carb
RESULTS: Copper .03 mg/L
C. Emily’s Purple
41.00 Potash Feldspar
12.00 Colemanite
7.00 Dolomite
15.00 Talc
5.00 Tennessee #5 Ball Clay
20.00 Silica
100.00 % Totals:
Also add:
2.00 Cobalt Oxide
2.00 Bentonite
2.00 Tin Oxide
RESULTS: COBALT .03
D. Strontium chun blue
Custer 48.8
EPK 1.5
Gerstley Borate 9.1
Dolomite 9.1
Whiting 2.7
Strontium 4.6
Zinc 1.8
Zircopax .6
Cobalt Carb .5
Rutile 5.2
RESULTS: Cobalt <.002 mg/L
Toni’s and Blue Ice
(Toni’s Copper over AE Blue Ice)
F. AE Blue Green
Laguna MG2 or White Waxy
Chrome
Cobalt
G. Delft Blue
Custer Spar 26.96
Whiting 19.20
EPK 19.60
Silica 32.24
Add Cobalt 250 (2.5%)
RESULTS: Cobalt .004
H. Red Glaze:
Basic clear glaze (CB, Vivika’s) + 4% de gussa light red
======================
(Partly Vivika Heino’s base glaze:
Custer Spar 27.48
EPK 19.95
Dolomite 19.57
Silica 32.94
And partly Carlton Ball clear:
Feldspar 250
EPK 200
Whiting 250
Silica 300
Plus 4% De Gussa light red
RESULTS: Cadmium .003 mg/L
I. AE Chun Blue
J. Long Beach Blue
Feldspar 63.55
Whiting 19.49
EPK 16.96
Cobalt 85
Rutile 400
RESULTS: Cobalt .004 mg/L
K. Baker Oribe
Oribe Cone 9-10 (BG ORIBE)
Bone ash 1.1
Talc 7.8
Whiting 22.4
Potash Feldspar 30.9
EPK kaolin 12.5
flint 25.3
+copper carbonate 5.5%
RESULTS: Copper .3
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