Mark Mondloch on tue 23 oct 01
> Probably no use in putting in the Zink Oxide if you are firing in
> reduction. There is reduction at some stages even in oxidation firing -
> especially if once firing - so even in oxidation firing it is probably
> vaporized.
Hi Ron,
I know this is conventional wisdom, but it doesn't seem to jibe with my
personal experience. I don't reduce heavily- short body reduction(10 min) at
cone 08, then neutral until glaze reduction. I use a high zinc rutile blue
glaze. I have tried removing the zinc from the recipe, but then it loses the
blue color. It also loses the blue color if reduced very heavily, but under
my normal firing conditions it doesn't. Could the zinc be somehow protected
from being volatized from reduction once it has started to be involved in
the glaze melt?
Awhile back I did a test. On a bisque plate I put a compacted teaspoon full
of each of the glaze ingredients that I normally use. I fired this plate
along with a normal glaze load. The little pile of zinc oxide shrunk in size
some but certainly did not disappear. Would you consider this a fair test to
see if the zinc is sticking around in my firings?
Actually, I'd recommend anyone doing this test with their own glaze
materials as it was very interesting to see how the individual materials act
all by themselves.
Sylvia
---
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake ,Wi 53075
HotArt@silvercreekpottery.com
http://www.silvercreekpottery.com
Jocelyn McAuley on tue 23 oct 01
Hi Sylvia
having you bring this up after the emails have been passed back and forth
has actually made me take the time to read about this issue (thanks).
I'm just kind of thinking out loud, so please correct me if I'm going down
some wrong paths:
A spectral analysis would tell you whether the zinc survives reduction. I
hope I'm remembering the correct name of the analysis. We did it in
organic lab alot. You grind up your substrate, push it into a pellet
form, and then excite your sample. Reading the energy outputs tells you
what molecules are present in your sample. These readouts are present in
many of Tichane's books analysing chinese glazes.
In regards to your experiement of putting the zinc straight through a
fire... You put it in a high fire right, not just a bisque? seems like
that should be zinc that is left (assuming your zinc oxide is not full of
impurities). My Handbook of Chemistry and Physics lists zinc oxide as
melting at 1975 degrees celsius.
Thinking back to my reduction experiments with crystalline glazes, I would
think the silica may "protect" the zinc molecules from vaporizing. The
silica and zinc bond to form zinc-silicate cystals. These crystals
don't disappear upon reduction on the cool down at 1500F... my handbook
lists these as melting at 1509 celsius so that makes alot of
sense. However word of mouth says that it's near impossible to form
crystals while firing in a reductive nature on your climb up in temp.
> > RR said:
> > Probably no use in putting in the Zink Oxide if you are firing in
> > reduction. There is reduction at some stages even in oxidation firing -
> > especially if once firing - so even in oxidation firing it is probably
> > vaporized.
>
> Hi Ron,
> I know this is conventional wisdom, but it doesn't seem to jibe with my
> personal experience. I don't reduce heavily- short body reduction(10 min) at
> cone 08, then neutral until glaze reduction. I use a high zinc rutile blue
> glaze. I have tried removing the zinc from the recipe, but then it loses the
> blue color. It also loses the blue color if reduced very heavily, but under
> my normal firing conditions it doesn't. Could the zinc be somehow protected
> from being volatized from reduction once it has started to be involved in
> the glaze melt?
>
> Awhile back I did a test. On a bisque plate I put a compacted teaspoon full
> of each of the glaze ingredients that I normally use. I fired this plate
> along with a normal glaze load. The little pile of zinc oxide shrunk in size
> some but certainly did not disappear. Would you consider this a fair test to
> see if the zinc is sticking around in my firings?
>
> Actually, I'd recommend anyone doing this test with their own glaze
> materials as it was very interesting to see how the individual materials act
> all by themselves.
> Sylvia
> ---
> Mark & Sylvia Mondloch
> Silver Creek Pottery & Forge
> W6725 Hwy 144
> Random Lake ,Wi 53075
> HotArt@silvercreekpottery.com
> http://www.silvercreekpottery.com
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
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>
--
Jocelyn McAuley ><<'> jocie@worlddomination.net
Eugene, Oregon
Alan D. Scott on sun 28 oct 01
Now I can really appreciate "metal fume fever" thanks to your description:
"...a flue-like feeling..." :-)
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Ron Roy
Sent: Saturday, October 27, 2001 21:27
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: RR vaporized zinc
Hi Sylvia,
I'm late with this but anyway -
As you explained - if you do a - shall I call it a "normal" reduction you
lose the blue colour - sounds to me like you lose the zinc because when you
omit the zinc you also loose the blue colour as well.
In your case - because you reduce so lightly - the zinc does not have a
chance to be reduced enough to leave.
Till we are able to predict which glazes are likely to seal over enough to
protect the zinc from being reduced - the best way to see if you are just
sending expensive zinc up the chimney - is to mix up a test lot of our zinc
bearing glazes and fire em up with a sample of it with zinc included beside
each other - if the batch is big enough and the zincless glaze is a big
batch and still needs the zinc - it can be added in.
Zinc oxide is usually mentioned as a possible pin hole maker. Those firing
zinc bearing glazes in oxidation and are having pin hole problems should
make sure:
1. Bisque firings are "clean" meaning all carbonous material is burned out
during the bisque firing and their is enough replacement oxygen.
2. Make sure that any combustibles - like wax - are cleared out during the
glaze fire.
A vent system is probably the best answer along with firings that are not
too fast. I guess I should add - a working vent system.
When I mentioned the test to see if a vent system was working I forgot
about the other kind - with the fan attached to the kiln - they still work
for the ware but will exhaust the kiln fumes to the room the kiln is in if
there are any holes in the flexible ducting. Mine has the fan just before
the chimney and the flexible ducting between the kiln and the fan.
If your zinc is volitizing you may wind up with metal fume fever - a flue
like feeling which will go away within a day or so. They say it is not a
serious health problem but not very enjoyable either.
RR
>> Probably no use in putting in the Zink Oxide if you are firing in
>> reduction. There is reduction at some stages even in oxidation firing -
>> especially if once firing - so even in oxidation firing it is probably
>> vaporized.
>
>Hi Ron,
>I know this is conventional wisdom, but it doesn't seem to jibe with my
>personal experience. I don't reduce heavily- short body reduction(10 min)
at
>cone 08, then neutral until glaze reduction. I use a high zinc rutile blue
>glaze. I have tried removing the zinc from the recipe, but then it loses
the
>blue color. It also loses the blue color if reduced very heavily, but under
>my normal firing conditions it doesn't. Could the zinc be somehow protected
>from being volatized from reduction once it has started to be involved in
>the glaze melt?
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
____________________________________________________________________________
__
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.
Ron Roy on sun 28 oct 01
Hi Sylvia,
I'm late with this but anyway -
As you explained - if you do a - shall I call it a "normal" reduction you
lose the blue colour - sounds to me like you lose the zinc because when you
omit the zinc you also loose the blue colour as well.
In your case - because you reduce so lightly - the zinc does not have a
chance to be reduced enough to leave.
Till we are able to predict which glazes are likely to seal over enough to
protect the zinc from being reduced - the best way to see if you are just
sending expensive zinc up the chimney - is to mix up a test lot of our zinc
bearing glazes and fire em up with a sample of it with zinc included beside
each other - if the batch is big enough and the zincless glaze is a big
batch and still needs the zinc - it can be added in.
Zinc oxide is usually mentioned as a possible pin hole maker. Those firing
zinc bearing glazes in oxidation and are having pin hole problems should
make sure:
1. Bisque firings are "clean" meaning all carbonous material is burned out
during the bisque firing and their is enough replacement oxygen.
2. Make sure that any combustibles - like wax - are cleared out during the
glaze fire.
A vent system is probably the best answer along with firings that are not
too fast. I guess I should add - a working vent system.
When I mentioned the test to see if a vent system was working I forgot
about the other kind - with the fan attached to the kiln - they still work
for the ware but will exhaust the kiln fumes to the room the kiln is in if
there are any holes in the flexible ducting. Mine has the fan just before
the chimney and the flexible ducting between the kiln and the fan.
If your zinc is volitizing you may wind up with metal fume fever - a flue
like feeling which will go away within a day or so. They say it is not a
serious health problem but not very enjoyable either.
RR
>> Probably no use in putting in the Zink Oxide if you are firing in
>> reduction. There is reduction at some stages even in oxidation firing -
>> especially if once firing - so even in oxidation firing it is probably
>> vaporized.
>
>Hi Ron,
>I know this is conventional wisdom, but it doesn't seem to jibe with my
>personal experience. I don't reduce heavily- short body reduction(10 min) at
>cone 08, then neutral until glaze reduction. I use a high zinc rutile blue
>glaze. I have tried removing the zinc from the recipe, but then it loses the
>blue color. It also loses the blue color if reduced very heavily, but under
>my normal firing conditions it doesn't. Could the zinc be somehow protected
>from being volatized from reduction once it has started to be involved in
>the glaze melt?
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
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