iandol on fri 27 oct 00
This is a request for information about observations which may have been =
made during or after a heavy reduction firings. I require these reports =
for a study into the nature of Reduction Firing which might bridge some =
of the gaps in our understanding of this process.
I wish to know if anyone had observed or recorded a build up of =
Electrostatic Charge on the surfaces of pots when they have been =
unloading ceramic wares after a heavy or any other sort of Reduction =
Firing.
This would be perceived as a light or slight crackling sensation when =
the pots were first touched. It would be insufficient to cause tingling =
or the sensation of an electric shock. It is not repeated in the same =
area after the pot has been touched with the bare hands. This is =
something the hot unloaders may not be aware of because they wear =
gloves.
The best way that I can describe it is to say that it was like breaking =
a fine crisp froth. But this was impossible since the surface remained =
absolutely smooth and there was no residue on my hands.
When I was firing with fuel oil and applied heavy reduction this was a =
common phenomenon with some of the pots I fired. It was experience when =
unloading cold pots from an 8cu ft. cross draught kiln. Occasionally I =
observed the same effect on gas fired salt glazed ware.
I wish to know if this effect has been noticed by anyone else, and if it =
has, their firing conditions including cone values, the style of their =
glazes, and in particular, the nature of the colorants they were using.=20
Looking forward to your reports,
Ivor Lewis. Redhill. South Australia.
Kathy McDonald on fri 27 oct 00
Hi,
Yes I have experienced that phenomenon.
Was quite pronounced with a copper red glaze
I had been using,,,needless to say I ditched the glaze.
Was curious about what caused it and the crusty foamy looking surface...
just chalked it up to another wierd pottery occurrence.
Caly was a porcelain...glaze if i remember correctly was
Andes Chun from Zakin's book made with strontium stead of barium.
Fired to cone 9 redux in a 50 cu ft propane fired downdraft.
but those pots were *charged* for sure...
Kathy Mc
http://www.willowtreepottery.com
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of iandol
Sent: Thursday, October 26, 2000 8:31 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Reduction Firing - Unusual Phenomena
This is a request for information about observations which may have been
made during or after a heavy reduction firings. I require these reports for
a study into the nature of Reduction Firing which might bridge some of the
gaps in our understanding of this process.
I wish to know if anyone had observed or recorded a build up of
Electrostatic Charge on the surfaces of pots when they have been unloading
ceramic wares after a heavy or any other sort of Reduction Firing.
This would be perceived as a light or slight crackling sensation when the
pots were first touched. It would be insufficient to cause tingling or the
sensation of an electric shock. It is not repeated in the same area after
the pot has been touched with the bare hands. This is something the hot
unloaders may not be aware of because they wear gloves.
The best way that I can describe it is to say that it was like breaking a
fine crisp froth. But this was impossible since the surface remained
absolutely smooth and there was no residue on my hands.
When I was firing with fuel oil and applied heavy reduction this was a
common phenomenon with some of the pots I fired. It was experience when
unloading cold pots from an 8cu ft. cross draught kiln. Occasionally I
observed the same effect on gas fired salt glazed ware.
I wish to know if this effect has been noticed by anyone else, and if it
has, their firing conditions including cone values, the style of their
glazes, and in particular, the nature of the colorants they were using.
Looking forward to your reports,
Ivor Lewis. Redhill. South Australia.
____________________________________________________________________________
__
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.
Sarah House on fri 27 oct 00
I have noticed this!! especially with my temmaku glaze. I also think that
two pots knocking together make a strange sound the first few hours out of
the kiln. Sort of a grating sound.
Sarah House
Snail Scott on fri 27 oct 00
I've mentioned this thread to my husband (PhD in physics).
He says he only wonders why it doesn't happen more often!
He speculates that the effect of the reduction in combination
with an iron-bearing glaze is creating a homemade version of
a 'Leyden jar' (a sort of primitive electrical storage device).
This is partly because of the shape of the object (hollow).
It doesn't have to be a 'jar' or 'bowl' shape, or even round;
it just needs to be somewhat hollow. Even hollow sculpture would
produce this effect. The other reason this happens is the glaze
formulation. In reduction, metallic oxides like copper and iron
become more truly metallic with the removal of oxygen and thus more
electrically conductive. The effect should also be stronger on
pieces glazed on the inside, as opposed to an outside-only glaze job.
He also suspects that matt surfaces might tend to discharge
into the air more readily during cooling, so glossy glazes
(like tenmoku) probably retain that charge slightly longer.
He also wonders if the quartz (silica) content may be creating
a piezoelectric phenomenon which is adding to the Leyden jar effect.
-Snail
At 02:18 AM 10/27/00 -0400, you wrote:
>I have noticed this!! especially with my temmaku glaze. I also think that
>two pots knocking together make a strange sound the first few hours out of
>the kiln. Sort of a grating sound.
>Sarah House
amy parker on fri 27 oct 00
Ivor - I have had a combination of two store-bought cone 6 glazes give me
that same kind of sensation - it makes a noise sort of like cellophane
being gathered. After I have run my fingers over the whole surface, the
noise goes away. This combination seems to not craze, even after
freeze/boil tests, but it sure is weird.
Amy
Amy Parker
Lithonia, GA
Mark Mondloch on fri 27 oct 00
iandol wrote:
if anyone had observed or recorded a build up of Electrostatic Charge on
the surfaces...
Ivor,
I've observed this often on the bottom side of the silicon carbide
shelves in my small wood fire kiln. Sometimes glazed pots under those
shelves do it too- I think especially my rutile blue.
Sylvia
--
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake, WI 53075
silvercreek@execpc.com
http://www.execpc.com/silvercreek
iandol on sat 28 oct 00
Dear Sylvia,
Thank you for coming forward with your information. I had not thought =
about the shelves being affected in that way. I did use silicon carbide =
shelves in my salt glaze kiln but never felt that effect on them.
Knowing that it was glazes with Rutile may be an important clue. Am I =
correct to think that you are doing a lot of reduction during your =
firings?
At least we are finding out that this may be a widespread phenomenon =
which has been ignored because it seems to be of no significance. I have =
cause to believe otherwise. Clayart seems to be a wonderful way to get =
these ideas openned up for dicussion.
My best regards,
Ivor.
Maid O'Mud Pottery on sat 28 oct 00
I have felt this phenomenom from time to time unloading my electric kiln. I fire to ^10 at 5 o'clock.
iandol wrote:
> This is a request for information about observations which may have been made during or after a heavy reduction firings. I require these reports for a study into the nature of Reduction Firing which might bridge some of the gaps in our understanding of this process.
>
> I wish to know if anyone had observed or recorded a build up of Electrostatic Charge on the surfaces of pots when they have been unloading ceramic wares after a heavy or any other sort of Reduction Firing.
>
> This would be perceived as a light or slight crackling sensation when the pots were first touched. It would be insufficient to cause tingling or the sensation of an electric shock. It is not repeated in the same area after the pot has been touched with the bare hands. This is something the hot unloaders may not be aware of because they wear gloves.
>
> The best way that I can describe it is to say that it was like breaking a fine crisp froth. But this was impossible since the surface remained absolutely smooth and there was no residue on my hands.
>
> When I was firing with fuel oil and applied heavy reduction this was a common phenomenon with some of the pots I fired. It was experience when unloading cold pots from an 8cu ft. cross draught kiln. Occasionally I observed the same effect on gas fired salt glazed ware.
>
> I wish to know if this effect has been noticed by anyone else, and if it has, their firing conditions including cone values, the style of their glazes, and in particular, the nature of the colorants they were using.
>
> Looking forward to your reports,
>
> Ivor Lewis. Redhill. South Australia.
>
> ______________________________________________________________________________
> 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.
--
sam - alias the cat lady
SW Ontario CANADA
http://www.geocities.com/paris/3110 scuttell@odyssey.on.ca
"Never attribute to malice, that which can be
explained by stupidity." anon
"First, the clay told me what to do
Then, I told the clay what to do
Now; we co-operate"
sam, 1994
MLL7777@AOL.COM on sun 29 oct 00
Dear Ivor,
I'm so glad you mentioned this phenomena. I was wondering what was going on.
I fired pots for my elementary students and this exact thing happened. It
only happened on some of the pots in the load...
electric - cone 06
cone 06 white clay
lots of blue underglaze - Amaco 06
clear glaze
some pinholing -
raw glazed with brush so the glaze layer was thin
soaked at 200 degrees
the electric charge seemed to be mostly near the shoulder of the pot where
the pinholes were and where the glaze was a bit thicker. once I wiped my
hand over it - it was gone. and the pots were cold when I took them from the
kiln.
looking forward to hearing your deduction...........
Mary Lou
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