Dan Dermer on sun 17 feb 02
One of my favorite c10 green glazes is not coming out like it used to...
Here is the recipe (originally posted by June Perry on Clayart in '96):
DEEP GREEN, c10 R
5 Bone ash
9 Gerstley Borate
5 Whiting
67 Kona F4 Soda Feldspar
14 Flint
Add:
5 Zinc oxide
2 Red Iron oxide
.25 Cobalt oxide
.50 Chrome oxide
In my first 2 firings, it came out a beautiful dark hunter green. I use it
on Laguna BMIX, fired to a flat cone 10 in light reduction from 010 to cone
9, then in neutral to oxidation until finished.
In the last 3 firings, it's coming out brown instead of green. After some
research, I mixed a new batch without the zinc oxide which supposedly turns
chrome greens to brown, but the result was the same brown color. Today I
plan to mix up a batch with the addition of 1-2% Zircopax, because
supposedly this will stabilize the Chrome Oxide, which I thought could be
volatizing out of the glaze. My last few firings were longer and fired to a
flatter cone 10 than the first two.
I also wondered if replacing some of the Kona with Custer feldspar would
allow the glaze to be fired slightly hotter, while keeping the colorants in
the glaze.
Any other suggestions? Tomorrow, I'll also be test-firing the same colorant
combination in two other glossy base glazes I like.
Thanks for any ideas,
Dan
p.s. A teapot in this glaze (coming out dark green) is pictured my home
page:
http://www.geocities.com/dbdermer
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Tom Buck on tue 19 feb 02
D.Dermer:
The behaviour of zinc oxide at high temperatures in a reducing
atmosphere has been discussed on Clayart, and you could check the archives
for this.
Yet, to get you over the hump, here is a glaze revision for you to
try:
Hunter (dark) green, Cone 10 reduction
56 Kona F-4 feldspar
8 Whiting
6 Gerstley borate (or FF 3124, Fusion F-19, Pemco P311)
4 Bone ash
26 Flint (silica, quartz)
add: 1.5 iron oxide red, 0.25 cobalt oxide, 0.50 chromium oxide
This version removes the zinc oxide and compensates for it by
boosting the other flux oxides. The two Seger formulas thus are closely
matched.
good tests. Peace, Tom B.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Dan Dermer on tue 19 feb 02
Tom,
Thanks for the info and recommendations...! I guess I'm still wondering why
the original glaze, with zinc oxide removed, was coming out brown. I had
three theories -- 1) too much reduction, or 2) too high temperature causing
chrome to volatize out of the glaze, or 3) too much RIO, making the glaze
brownish.
Current tests in the kiln include two variations on 4-3-2-1 glaze bases,
plus original Kona-base glaze (sans zinc) with the following altered
colorant combo:
1.0 RIO
.5 Cobalt Carb
.5 Chrome Oxide
2.0 Zircopax
Anyhow, I'm looking forward to testing the reformulated version you provided
in my next firing. Will definitely report back.
Thanks again,
Dan
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Dan Dermer on sat 22 jun 02
Well, 4 months later...
I thought I would post my results in attempting to find a nice cone 10
reduction, dark green glossy glaze with depth. The formula below is the one
I liked best, based on the base glaze for Coleman Purple, but zinc oxide
removed:
Dark Forest Green, c10R (TEST TILE #3)
50.90% Custer
5.12% Barium Carb
5.12% Gerstley Borate
25.58% Flint
8.18% Whiting
5.12% Dolomite
100.00%
Also add:
2.00% Red Iron Oxide
0.50% Cobalt Carb
0.50% Chrome Oxide
2.00% Bentonite
Check out a picture of Dark Forest Green, c10R on TEST TILE #3 (& other
trials):
1. Surf to http://photos.yahoo.com/dbdermer
2. Click on "Glaze Tests"
3. Click on the picture itself to enlarge...
Here are the recipes for test other tiles pictured, with comments.
TEST TILE #1 - "Waxy Turquoise"
Flint 19.8
Custer 40.59
EPK 4.95
Talc 14.85
Gerst-Bor. 11.88
Dolomite 6.93
Chrome Ox. 0.5
Cobalt Ox. 0.5
Add
Bentonite 2.00
(Excellent satin matt, extremely smooth glaze surface. Looks great on white
stoneware as well as darker red stoneware).
TEST TILE #2 - "Deep Green"
(posted by Lesley Alexander on Clayart, 5/7/2002 -- subject "White glazes")
Same base as Waxy Turquoise above, but with these colorants:
.3 cobalt carb, .9875% chrome, .75% yellow iron oxide
It came out an olive green (sage) color for me, with that excellent satin
matt. Not what I was looking for, but an okay glaze.
TEST TILE #4
Same base as TEST TILE #1, but with colorants of Lesley Alexander's glaze:
.3 cobalt carb, .9875% chrome, .75% yellow iron oxide
It's a nice glossy turquoise (teal). If I didn't already love the buttery
surface and color of "Waxy Turqouise", I might try using this glaze. But...
it was not what I was looking for, and I felt the color was a little too
saturated.
==================
Thanks to all who chimed in back in February with suggestions...!
-Dan
Ron Roy on mon 24 jun 02
This looks like it may be a durable glaze - if you don't like using Barium
simply replace it with 4 Strontium. It should still be tested with lemon on
it for a few days to make sure it does not discolour.
The second one I am not so sure of - we have no data on the durability of
cone 10 glazes - yet - on the other hand not much to worry about in the
glaze except if it changes colour when in contact with food.
RR
>Dark Forest Green, c10R (TEST TILE #3)
>50.90% Custer
>5.12% Barium Carb
>5.12% Gerstley Borate
>25.58% Flint
>8.18% Whiting
>5.12% Dolomite
>100.00%
> Also add:
>2.00% Red Iron Oxide
>0.50% Cobalt Carb
>0.50% Chrome Oxide
>2.00% Bentonite
>
>Check out a picture of Dark Forest Green, c10R on TEST TILE #3 (& other
>trials):
>1. Surf to http://photos.yahoo.com/dbdermer
>2. Click on "Glaze Tests"
>3. Click on the picture itself to enlarge...
>
>Here are the recipes for test other tiles pictured, with comments.
>
>TEST TILE #1 - "Waxy Turquoise"
>Flint 19.8
>Custer 40.59
>EPK 4.95
>Talc 14.85
>Gerst-Bor. 11.88
>Dolomite 6.93
>Chrome Ox. 0.5
>Cobalt Ox. 0.5
>Add
>Bentonite 2.00
>(Excellent satin matt, extremely smooth glaze surface. Looks great on white
>stoneware as well as darker red stoneware).
>
>TEST TILE #2 - "Deep Green"
>(posted by Lesley Alexander on Clayart, 5/7/2002 -- subject "White glazes")
>Same base as Waxy Turquoise above, but with these colorants:
>.3 cobalt carb, .9875% chrome, .75% yellow iron oxide
>
>It came out an olive green (sage) color for me, with that excellent satin
>matt. Not what I was looking for, but an okay glaze.
>
>TEST TILE #4
>Same base as TEST TILE #1, but with colorants of Lesley Alexander's glaze:
>.3 cobalt carb, .9875% chrome, .75% yellow iron oxide
>
>It's a nice glossy turquoise (teal). If I didn't already love the buttery
>surface and color of "Waxy Turqouise", I might try using this glaze. But...
>it was not what I was looking for, and I felt the color was a little too
>saturated.
>
>==================
>
>Thanks to all who chimed in back in February with suggestions...!
>-Dan
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Daniel Dermer on fri 28 jun 02
David,
Thanks for finding this discrepancy in my post...
Indeed, TEST TILE #4 uses the glossy base glaze as
Coleman Purple (TEST TILE #3, not #1).
My notes about it should read:
TEST TILE #4
Same base as TEST TILE #3, but with colorants of
Lesley Alexander's glaze:
.3 cobalt carb, .9875% chrome, .75% yellow iron oxide
It's a nice glossy turquoise (teal). If I didn't
already love the buttery surface and color of "Waxy
Turqouise", I might try using this glaze.
--- Original Message ---
From: "David Hendley"
To: "\"Dan Dermer\""
Subject: Re: chrome green glaze question
>I'm confused. According to your descriptions below,
>test #2 and test #4 are exactly the same. The test
tiles,
>however, are totally different.
>If you have a minute will you explain? I think #4 is
nice,
>and might try it.
>
>Thanks,
>David Hendley
>Maydelle, Texas
>hendley@tyler.net
>http://www.farmpots.com
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