Paulette Carr on sat 7 may 05
I submitted this request yesterday, but for some reason, it
disappeared into cyberspace. So, at the risk of being redundant,
"here goes again":
I am looking for a recipe that was published in the Nov./Dec. '02
issue of Clay Times called "Black Breakthrough Glaze 9-11 (Phil
May). Unfortunately, I cannot locate my copy of the magazine, and
this appears to be a soldout issue. If anyone has a copy of this
issue, and wouldn't mind sending the recipe, I would be very
grateful!!! You can contact me on or off list.
Thanks, in advance, for your help!
My best,
Paulette Carr
Paulette Carr Studio
Member/Potters Council
St. Louis, MO
gan8qj88@juno.com on sat 7 may 05
Hi to all!
Black Breakthrough Glaze ^9-11
Whiting.......................16.5
Zinc Oxide.....................2.2
Potash feldspar...............48.5
E P K.........................10.2
Flint.........................22.6
Total......100.0
add Bentonite..................1.0
RIO 9.7
used by Phil May-----Comment: This is a lovely rust color when
applied thinly,and a deep black-brown when applied thickly.
Phil May uses this glaze in all areas of his wood kiln.
John Britt on sat 7 may 05
Paulette,
That glaze is a Temmoku and is very similar to the Rust Black in my book.
RUST BLACK Cone 10
Custer Feldspar 46.23
Silica 23.24
Whiting 17.40
EPK Kaolin 10.86
Zinc Oxide 2.27
Red Iron Oxide 11.20
Black Breakthrough Cone 10
Custer Feldspar 48.5
Silica 22.6
Whiting 16.5
EPK Kaolin 10.2
Zinc Oxide 2.2
Red Iron Oxide 9.7
Hope it helps,
John Britt
www.johnbrittpottery.com
Ron Roy on wed 11 may 05
Hi John,
I'm curious - I would think the zinc would be gone at the end of a
reduction firing - have you tried this glaze without the zinc?
RR
>That glaze is a Temmoku and is very similar to the Rust Black in my book.
>
>
>RUST BLACK Cone 10
>
>
>Custer Feldspar 46.23
>Silica 23.24
>Whiting 17.40
>EPK Kaolin 10.86
>Zinc Oxide 2.27
>
>Red Iron Oxide 11.20
>
>
>Black Breakthrough Cone 10
>
>
>Custer Feldspar 48.5
>Silica 22.6
>Whiting 16.5
>EPK Kaolin 10.2
>Zinc Oxide 2.2
>
>Red Iron Oxide 9.7
>John Britt
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Britt on wed 11 may 05
Ron,
I have not tried the glaze without zinc oxide. I was merely replying to
her request for a glaze recipe.
I have fired it in oxidation and it is a nice temmoku.
I would assume that in reduction the zinc oxide would be gone but I don't
know that for certain. I have never tested for its presence after a
firing. I have fired a melt test of zinc in both a heavy reduction
atmosphere and full oxidation and the reduced sample disappears, while the
oxidized sample remains.
But I don't know if the zinc oxide could melt early in the firing (in
oxidizing conditions) and then enter into some silicate structure which
would allow it to remain after the reduction period. Have you ever tested
for the presence of zinc in a glaze after a firing?
John Britt
www.johnbrittpottery.com
John
www.johnbrittpottery.com
Craig Martell on wed 11 may 05
RR was asking:
>I'm curious - I would think the zinc would be gone at the end of a
>reduction firing - have you tried this glaze without the zinc?
Hello Ron:
I sent a post on this glaze last week because I regognized it as a rounded
off version of Harlan House's glaze, Peach Black. PB is a tenmoku that
I've used for probably 20 years or so. I took out the zinc and it fired
exactly the same as if I'd kept the zinc in the glaze. Then I added some
more silica for glaze fit and it was even better on my clays. Anyway, for
whatever it's worth, that's my take on this glaze.
regards, Craig Martell Hopewell, Oregon
Ron Roy on fri 13 may 05
Hi John,
I assume you saw Craigs post on this and that this glaze does not need the
ZnO in reduction - and for the same reason - not in oxidation either.
David Hendley dida bunch of testing - wrote an article for CM I think -
took a bunch of copper reds with ZnO in them and they all fired fine
without it.
He also did some other experiments and found some glazes that still needed
it - even in reduction - there was no explanation - I can only speculate
that the glazes that retained some or all of the ZnO had sealed over before
reduction started - perhaps a glaze with enough boron would be that kind.
I don't know if that is the answer you are looking for.
I wonder why anyone would include zinc in a reduction glaze to start with -
could it be that we lost some essential understanding of our materials over
the last 100 years?
RR
>I have not tried the glaze without zinc oxide. I was merely replying to
>her request for a glaze recipe.
>
>I have fired it in oxidation and it is a nice temmoku.
>
>I would assume that in reduction the zinc oxide would be gone but I don't
>know that for certain. I have never tested for its presence after a
>firing. I have fired a melt test of zinc in both a heavy reduction
>atmosphere and full oxidation and the reduced sample disappears, while the
>oxidized sample remains.
>
>But I don't know if the zinc oxide could melt early in the firing (in
>oxidizing conditions) and then enter into some silicate structure which
>would allow it to remain after the reduction period. Have you ever tested
>for the presence of zinc in a glaze after a firing?
>
>John Britt
>www.johnbrittpottery.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
John Britt on fri 13 may 05
Ron,
No one has said that this glaze was for reduction. I merely gave the
recipe someone asked for. I am not promoting or trying to do anything
other than providing a recipe.
I did see Craig=92s post. But you said: =93I assume you saw Craig=92s post o=
n
this and that this glaze does not need the ZnO in reduction - and for the
same reason - not in oxidation either=94.
Unless I missed it, there is no reason given that ZnO is not needed. In
fact, I don=92t know how Craig fires! I don=92t believe he said. So I don=92=
t
follow your logic.
You appear to be arguing both sides of the issue. David H. found some
glazes did not need the ZnO and others did. There was not explanation nor
was the research meant to be definitive. But he did not conclude that the
Zinc Oxide was unnecessary. And he certainly did not conclude that it was
unnecessary in oxidation.
Secondly, since you appear to have such a strong opinion on ZnO in
reduction glazes, I though you might have come across some research or
have done some testing of your own to back it up. But I guess not? So we
appear to be back to the conclusion that we don=92t know if zinc oxide is
necessary in a glaze, (oxidation or reduction) or how it functions in the
glaze melt.
I don=92t know if we =93lost some essential understanding of our materials
over the last 100 years?=94 I did not formulate the recipe nor do I use it.
I do not take it upon myself to adjust every recipe that I see to my
liking. And since even you don=92t have a clear understanding of Zinc Oxide
and its presence after the firing, I would say that perhaps we don't now,
and never did have a complete understanding of our materials over the last
100 years.
Confused,
John Britt
www.johnbrittpottery.com
Craig Martell on sat 14 may 05
Hello John:
I hope this will help.
When I responded to Ron's query about ZnO I was talking about the fact that
"Black Breakthrough" was actually Harlan House's glaze, Peach Black. I've
used this one for a long time and removed the ZnO. I fire to cone 10 in
reduction.
I saw no change at all in the glaze without the ZnO and I've never heard or
read of any advantage or reasons for using Zinc in a reduction
glaze. Especially in such small amounts. However, I think it was Tom Buck
who wrote a post on this sometime back saying that Zinc might remain in a
reduction glaze if fusion had commenced prior to reduction. I'm not sure
about this though.
regards, Craig Martell Hopewell, Oregon
Earl Brunner on sat 14 may 05
I remember some of the discussion wasn't so much whether or not the ZnO REMAINED in the glaze, but rather if it contributed anything to the melt and overall appearance of the final glaze, regardless of whether or not any of it remained in the final glaze in a reduction firing. In some glazes, some people felt that the final glaze was different when the ZnO was in the initial mix (even though it might reduce out during reduction) than when the ZnO was removed from the original batch. I'm sure this wasn't the case with ALL glazes, only some.
Craig Martell wrote:Hello John:
I hope this will help.
When I responded to Ron's query about ZnO I was talking about the fact that
"Black Breakthrough" was actually Harlan House's glaze, Peach Black. I've
used this one for a long time and removed the ZnO. I fire to cone 10 in
reduction.
I saw no change at all in the glaze without the ZnO and I've never heard or
read of any advantage or reasons for using Zinc in a reduction
glaze. Especially in such small amounts. However, I think it was Tom Buck
who wrote a post on this sometime back saying that Zinc might remain in a
reduction glaze if fusion had commenced prior to reduction. I'm not sure
about this though.
regards, Craig Martell Hopewell, Oregon
______________________________________________________________________________
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Earl Brunner
e-mail: brunv53@yahoo.com
sincultura13 on sun 15 may 05
I found this link in the archive:
http://www.potters.org/subject55838.htm
Tom Bucks Explains:
"the ZnO does disappear when moderate to heavy reduction is carried
out ....
BUT ZnO is a strong flux that kicks in early and brings about a
melt earlier on than would occur if it were absent. So, some ZnO can
help
some glazes by making the liquidus (molten glass) appear at a
lowercone
and therefore allow some time for the slow gas/liquid reactions to
occur. "
BTW, I know nothing about the subject... I just found it and am
posting it in case it is of any help...
later,
Sincultura
--- In clayart@yahoogroups.com, John Britt wrote:
> Ron,
>
> No one has said that this glaze was for reduction. I merely gave
the
> recipe someone asked for. I am not promoting or trying to do
anything
> other than providing a recipe.
>
> I did see Craig's post. But you said: "I assume you saw Craig's
post on
> this and that this glaze does not need the ZnO in reduction - and
for the
> same reason - not in oxidation either".
>
> Unless I missed it, there is no reason given that ZnO is not
needed. In
> fact, I don't know how Craig fires! I don't believe he said. So I
don't
> follow your logic.
>
> You appear to be arguing both sides of the issue. David H. found
some
> glazes did not need the ZnO and others did. There was not
explanation nor
> was the research meant to be definitive. But he did not conclude
that the
> Zinc Oxide was unnecessary. And he certainly did not conclude that
it was
> unnecessary in oxidation.
>
> Secondly, since you appear to have such a strong opinion on ZnO in
> reduction glazes, I though you might have come across some
research or
> have done some testing of your own to back it up. But I guess not?
So we
> appear to be back to the conclusion that we don't know if zinc
oxide is
> necessary in a glaze, (oxidation or reduction) or how it functions
in the
> glaze melt.
>
> I don't know if we "lost some essential understanding of our
materials
> over the last 100 years?" I did not formulate the recipe nor do I
use it.
> I do not take it upon myself to adjust every recipe that I see to
my
> liking. And since even you don't have a clear understanding of
Zinc Oxide
> and its presence after the firing, I would say that perhaps we
don't now,
> and never did have a complete understanding of our materials over
the last
> 100 years.
>
> Confused,
>
> John Britt
> www.johnbrittpottery.com
>
>
_____________________________________________________________________
_________
> Send postings to clayart@l...
>
> You may look at the archives for the list or change your
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> settings from http://www.ceramics.org/clayart/
>
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