william schran on tue 22 oct 02
Ilene - If you didn't use calcined zinc in your crystalline glazes
you'd probably have to also deal with crawling. Should try samples of
zinc from different sources before you blame the zinc. I calcine my
zinc in the bisque firing cause I know the stuff absorbs moisture out
of the air.
Bill
Jocelyn McAuley on tue 22 oct 02
On Tue, 22 Oct 2002, Ilene Mahler wrote:
> I just tried the Trinity Zinc Oxide calcined that I ordered a sample from last
year it was sealed in paper in a plastic bag.Made up 1500 grams of 2 glazes
because it was going to work... went through my 80 mesh tailsman like a dream..
Fired 14hours and 43 min. a 5+ hour soak not only no ctystals on those pieces
at all but a teapot refiring broke off its pedistal and wiped out all the
pieces together in one large sculpture the only good thing nothing stuck to
the shelf and I didn't cut my self taking it out of the kiln,There were
maybe 6 salable pieces...I HATE CALCINED ZINC OXIDE...Someone out there
prove me wrong...PLEASE!!!!! A topic for discussion at San Diego...Ilene in Conn
Ilene, I really don't hear anything in your email that fingers Zinc as the
culprit in your situation. Unless you're throwing this zinc into your
clay body?
is your seeding temperature the same?
Is this the same firing schedule you have used for REFIRES in the past?
Are the teapot and the pedestal made from the same clay body? Both in the
same state (shrinkage problems with an already highfired piece on a
bisqued pedestal, etc)?
You say you have 6 salable pieces- do these have crystals?
If you have no crystals at all in the batch and zinc is the ONLY variable
you have changed... maybe the zinc is the problem. But from what you have
shared, it's difficult to deduce that.
Hope venting here has helped a bit.
I wish you the best of luck!
Jocelyn
--
Jocelyn McAuley ><<'> jocie@worlddomination.net
Eugene, Oregon http://www.ceramicism.com
Ilene Mahler on tue 22 oct 02
I just tried the Trinity Zinc Oxide calcined that I ordered a sample =
from last year it was sealed in paper in a plastic bag.Made up 1500 =
grams of 2 glazes because it was going to work... went through my 80 =
mesh tailsman like a dream..Fired 14hours and 43 min. a 5+ hour soak not =
only no ctystals on those pieces at all but a teapot refiring broke off =
its pedistal and wiped out all the pieces together in one large =
sculpture the only good thing nothing stuck to the shelf and I didn't =
cut my self taking it out of the kiln,There were maybe 6 salable =
pieces...I HATE CALCINED ZINC OXIDE...Someone out there prove me =
wrong...PLEASE!!!!! A topic for discussion at San Diego...Ilene in Conn
Ilene Mahler on wed 23 oct 02
Whose are you using..I though that I would get lazy and us the pre...but..I
guess that I will pre-sieve the calcined that I make from Laguna...Ilene
----- Original Message -----
From: william schran
To:
Sent: Tuesday, October 22, 2002 5:41 PM
Subject: Re: The same old song.Zinc oxide
> Ilene - If you didn't use calcined zinc in your crystalline glazes
> you'd probably have to also deal with crawling. Should try samples of
> zinc from different sources before you blame the zinc. I calcine my
> zinc in the bisque firing cause I know the stuff absorbs moisture out
> of the air.
> Bill
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Ilene Mahler on wed 23 oct 02
okay heres' the deal the pieces that got georgous crystals are glazes from
Laguna zinc that I calcified .Trinity it already calcined..They were in the
same kiln even near each other.I was hoping not to calcine the Zinc and
pre-sift it.as there is always some that do not go through the 80
mesh...Ilene
----- Original Message -----
From: Jocelyn McAuley
To:
Sent: Wednesday, October 23, 2002 1:28 AM
Subject: Re: The same old song.Zinc oxide
> On Tue, 22 Oct 2002, Ilene Mahler wrote:
>
> > I just tried the Trinity Zinc Oxide calcined that I ordered a sample
from last
> year it was sealed in paper in a plastic bag.Made up 1500 grams of 2
glazes
> because it was going to work... went through my 80 mesh tailsman like a
dream..
> Fired 14hours and 43 min. a 5+ hour soak not only no ctystals on those
pieces
> at all but a teapot refiring broke off its pedistal and wiped out all the
> pieces together in one large sculpture the only good thing nothing stuck
to
> the shelf and I didn't cut my self taking it out of the kiln,There were
> maybe 6 salable pieces...I HATE CALCINED ZINC OXIDE...Someone out there
> prove me wrong...PLEASE!!!!! A topic for discussion at San Diego...Ilene
in Conn
>
> Ilene, I really don't hear anything in your email that fingers Zinc as the
> culprit in your situation. Unless you're throwing this zinc into your
> clay body?
>
> is your seeding temperature the same?
>
> Is this the same firing schedule you have used for REFIRES in the past?
>
> Are the teapot and the pedestal made from the same clay body? Both in the
> same state (shrinkage problems with an already highfired piece on a
> bisqued pedestal, etc)?
>
> You say you have 6 salable pieces- do these have crystals?
>
> If you have no crystals at all in the batch and zinc is the ONLY variable
> you have changed... maybe the zinc is the problem. But from what you have
> shared, it's difficult to deduce that.
>
> Hope venting here has helped a bit.
> I wish you the best of luck!
>
> Jocelyn
> --
> Jocelyn McAuley ><<'> jocie@worlddomination.net
> Eugene, Oregon http://www.ceramicism.com
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
John Hesselberth on wed 23 oct 02
I have to admit I never understood the concept of calcining zinc oxide.
If it absorbs moisture out of the air which results in crawling problems
will it not reabsorb moisture in the glaze bucket?? I mean they usually
are wet. This is not clay which undergoes a non reversible chemical
reaction on firing. In addition my Handbook of Chemistry and Physics
does not even show a hydrated form of zinc oxide. Are we not dealing
with a bit of potter's myth here? Yes, I know Hamer and Hamer say to
calcine it before use to minimize its shrinkange. They also say that, if
damp, it will eventually turn into the carbonate, but that it has a
shelf life of about 15 years. So what is the mechanism here? Will some
of the scientists on the list help this simple engineer, turned potter,
understand this?
Regards,
John
On Tuesday, October 22, 2002, at 05:41 PM, william schran wrote:
> I calcine my
> zinc in the bisque firing cause I know the stuff absorbs moisture out
> of the air.
http://www.frogpondpottery.com
http://www.masteringglazes.com
Fabienne Micheline Cassman on fri 25 oct 02
I use the following site for reference; it says that zinc does not react
with water.
http://www.webelements.com/webelements/elements/text/Zn/chem.html
However, it says something about [Zn(OH2)6]^2+ and [Zn(OH)4]^2- in
conjunction with acid and aqueous alkalis, respectively (pardon my winged
ascii notation). I have little understanding of chemistry, but it looks
like water is at work. Could acidity (pollution) in the air or its
moisture account for this and the alkaline base could be accounted for in
the glaze mix?
Just a thought,
Fabienne
At 08:21 PM 10/23/2002 -0400, you wrote:
>
>does not even show a hydrated form of zinc oxide. Are we not dealing
>with a bit of potter's myth here? Yes, I know Hamer and Hamer say to
>
Fabienne Cassman http://www.milkywayceramics.com/
WARNING: I cannot be held responsible for the above
because my cats have apparently learned to type.
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/_ \'. __..-' , ,--...--'''
<\ .`--''' ` /'
`-';' ; ; ;
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Alan D. Scott on fri 25 oct 02
Fabienne:
The zinc hydroxide complexes you so carefully typed in ASCII are produced
from elemental/metallic zinc (Zn) when reacted with potassium hydroxide
(KOH, a very strong alkali, very similar to sodium hydroxide NaOH = lye). A
solution of KOH would be VERY caustic. Unless you are using an unwashed ash
glaze with a lot of lye in it, the conditions needed would not exist in your
glaze bucket. Besides that, your glaze contains zinc oxide, not metallic
zinc.
Zinc oxide (ZnO) we potters work with is reasonably stable. Sometimes, a
potter buys zinc oxide and ends up with ZnO2, which reverts to ZnO when
heated to 150oC. I don't know much about "calcining" zinc, but it makes
sense to me that the potter who obtained ZnO2 and "calcined" it may think
that they have driven off some water, making it more suited to glazing.
However, in the change from ZnO2 to ZnO, only oxygen (O) is given off, not
water (H2O).
Chemistry class dismissed :-)
Alan Scott
Parker, AZ
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Fabienne Micheline Cassman
Sent: Thursday, October 24, 2002 10:21 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: The same old song.Zinc oxide
I use the following site for reference; it says that zinc does not react
with water.
http://www.webelements.com/webelements/elements/text/Zn/chem.html
However, it says something about [Zn(OH2)6]^2+ and [Zn(OH)4]^2- in
conjunction with acid and aqueous alkalis, respectively (pardon my winged
ascii notation). I have little understanding of chemistry, but it looks
like water is at work. Could acidity (pollution) in the air or its
moisture account for this and the alkaline base could be accounted for in
the glaze mix?
Just a thought,
Fabienne
At 08:21 PM 10/23/2002 -0400, you wrote:
>
>does not even show a hydrated form of zinc oxide. Are we not dealing
>with a bit of potter's myth here? Yes, I know Hamer and Hamer say to
>
Fabienne Cassman http://www.milkywayceramics.com/
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