Sam Wild on fri 20 apr 01
----- Original Message -----
From: "ILENE MAHLER"
To:
Sent: Friday, April 20, 2001 1:11 PM
Subject: Bad Zinc oxide
> I opened the kiln and no chrystals except for the pieces that didn't
> make the last load....My large bowl looked like bloat...What could it be
> just on bowls? Never use old chemicals even if they are marked I should
> of realized something was wrong when it shrank to half in the calcifying
> and the rock lumps...I have 25 lbs I hope being delivered today....Ilene
> in Sunny Conn which may reach 70 on Sun.
>
> When I calcine zinc oxide, it shrinks at least that much and has some
hard lumps in it. I grind it up in old grain grinder that I bought cheap in
a junk shop and then ball mill that and screen it through a 200 mesh screen
then dry it out so I can wiegh it. At that point it has light yellow shade
to it. Maybe you didn't reduce the zinc to a smll enough partical size.
That,s a lot of work, so I'm buying calcined zinc from now on.
Sam Wild
> Send postings to clayart@lsv.ceramics.org
>
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>
Jocelyn McAuley on fri 20 apr 01
Hi Ilene,
Perhaps if you elaborate a bit more on what you mean by:
> I opened the kiln and no chrystals except for the pieces that didn't
> make the last load...
we could help you more. Are you saying that in the same firing with the
same glaze recipe and the same colorants, you had some pieces with
crystals and some with out? How did your glaze sieve? Did you not
include all the rock hard zinc chunks- and therefore eliminated a large
portion of your zinc?
I've found that the same recipe with different oxides have different
crystal growing ranges, so maybe you hit the right range for some of the
oxides, and not for the other ones.
I've had difficulties with the zinc oxide in our studio glaze lab. After
calcining it (cone 06) I too have had rock hard lumps. I dry sieve my
zinc and grind down the lumps in a mortar and pestle until they pass thru
the sieve. Interestingly I broke into a new bag of zinc oxide after being
frustrated with the older zinc- hoping it would not have the rock lump
problem. This new zinc shrank almost to half its size, came out yellower,
and still had lumps! I did however make crystals (whew!).
One thing I have yet to try to prevent the zinc lumps is to try calcining
to a lower temperature.
Good Luck!
Jocelyn
--
Jocelyn McAuley ><<'> jocie@worlddomination.net
Eugene, Oregon
ILENE MAHLER on fri 20 apr 01
I opened the kiln and no chrystals except for the pieces that didn't
make the last load....My large bowl looked like bloat...What could it be
just on bowls? Never use old chemicals even if they are marked I should
of realized something was wrong when it shrank to half in the calcifying
and the rock lumps...I have 25 lbs I hope being delivered today....Ilene
in Sunny Conn which may reach 70 on Sun.
Brad Sondahl on sat 21 apr 01
In oxidation, pots which look bloated are generally overfired. You
might check to make sure all your elements are working.
I don't know why you are opposed to old glaze chemicals--except a few
like Zinc that absorb moisture and clump up (which can be avoided by
tightly sealing the plastic bag), most glaze chemicals are highly
stable. I use 25 year old chemicals regularly (and mourn having to buy
new and different ones).
I'm not sure what you are referring to about the shrinkage and
calcifying--do you mean the bisque fire?
Brad Sondahl
I opened the kiln and no chrystals except for the pieces that didn't
make the last load....My large bowl looked like
bloat...What could it be
just on bowls? Never use old chemicals even if they are
marked I should
of realized something was wrong when it shrank to half
in the calcifying
and the rock lumps...I have 25 lbs I hope being
delivered today....Ilene
in Sunny Conn which may reach 70 on Sun.
--
For original art, music, pottery, and literature, visit my homepage
http://pages.about.com/bsondahl
Pottery homepage http://sondahl.freeyellow.com
ILENE MAHLER on sat 21 apr 01
In chrysal glaze you must calcify the zinc oxide..Thats what I had the
problem as far as over fire I had the kiln at 2300 and it happened only
on bowl forms not tall forms any help would be appreciated as I love to
make bowl forms..Ilene in Conn
Brad Sondahl wrote:
>
> In oxidation, pots which look bloated are generally overfired. You
> might check to make sure all your elements are working.
> I don't know why you are opposed to old glaze chemicals--except a few
> like Zinc that absorb moisture and clump up (which can be avoided by
> tightly sealing the plastic bag), most glaze chemicals are highly
> stable. I use 25 year old chemicals regularly (and mourn having to buy
> new and different ones).
> I'm not sure what you are referring to about the shrinkage and
> calcifying--do you mean the bisque fire?
> Brad Sondahl
>
> I opened the kiln and no chrystals except for the pieces that didn't
> make the last load....My large bowl looked like
> bloat...What could it be
> just on bowls? Never use old chemicals even if they are
> marked I should
> of realized something was wrong when it shrank to half
> in the calcifying
> and the rock lumps...I have 25 lbs I hope being
> delivered today....Ilene
> in Sunny Conn which may reach 70 on Sun.
>
> --
> For original art, music, pottery, and literature, visit my homepage
> http://pages.about.com/bsondahl
> Pottery homepage http://sondahl.freeyellow.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.
ILENE MAHLER on sat 21 apr 01
Yes I was unable to get the rocks to a fine powere and not knowing how
much it was I just left it out..Probable not enough zinc I bisque to 08
Do you have any problems with bowl forms in chrystal with bloating or
maybe airbubbles broken and though were gone? I have more zinc going in
on Mon..The chrystal that formed were on pots that did not make in the
last kiln...Ilene in Conn Thanks for all your help in advance
Jocelyn McAuley wrote:
>
> Hi Ilene,
>
> Perhaps if you elaborate a bit more on what you mean by:
>
> > I opened the kiln and no chrystals except for the pieces that didn't
> > make the last load...
>
> we could help you more. Are you saying that in the same firing with the
> same glaze recipe and the same colorants, you had some pieces with
> crystals and some with out? How did your glaze sieve? Did you not
> include all the rock hard zinc chunks- and therefore eliminated a large
> portion of your zinc?
>
> I've found that the same recipe with different oxides have different
> crystal growing ranges, so maybe you hit the right range for some of the
> oxides, and not for the other ones.
>
> I've had difficulties with the zinc oxide in our studio glaze lab. After
> calcining it (cone 06) I too have had rock hard lumps. I dry sieve my
> zinc and grind down the lumps in a mortar and pestle until they pass thru
> the sieve. Interestingly I broke into a new bag of zinc oxide after being
> frustrated with the older zinc- hoping it would not have the rock lump
> problem. This new zinc shrank almost to half its size, came out yellower,
> and still had lumps! I did however make crystals (whew!).
>
> One thing I have yet to try to prevent the zinc lumps is to try calcining
> to a lower temperature.
>
> Good Luck!
> Jocelyn
>
> --
> Jocelyn McAuley ><<'> jocie@worlddomination.net
> Eugene, Oregon
>
> ______________________________________________________________________________
> 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.
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