mel jacobson on tue 30 oct 01
i do not think the glaze is eating into your shelf.
it is stuck tight, and when you pull off the pot
some of the shelf comes with it.
yes, itc will help, but i would do something about
the runny glaze. it does not have to run that much.
i know ash glazes move....but not all over the shelf.
in this case, i would take linda's suggestion.
itc heavy coat.
set your ash pots on silica sand, or flint. or, a good alumina
hydrate kiln wash.
in fact.....susan karrisch when doing her tests and
runny glazes......places them on a paper thin piece of porcelain.
it works like a charm. just roll out clay...thin. make a catcher
like the crystal glaze folks do.
anyway....yes, itc first.
max protection.
then add more protection/
cannot be too safe nowa days.
mel
From:
Minnetonka, Minnesota, U.S.A.
web site: http://www.pclink.com/melpots
Snail Scott on tue 30 oct 01
At 05:18 AM 10/30/01 -0600, Mel wrote:
>i do not think the [ash] glaze is eating into your shelf.
>it is stuck tight, and when you pull off the pot
>some of the shelf comes with it.
>
When I was a studio assistant in college, a student
built a sculptural project, then discovered it was
too fragile to move. So, she loaded it into the kiln
still on its plywood board. She also put sand under
the board. Apparently she had seen people do that
(to reduce friction with the shelf,) but hadn't
understood why. She then fired to ^10. No one knew
'til afterward.
Apparently the wood ash fluxed the silica sand.
The shelves (three 13"x26" mullite ones) were lightly
glazed across their surfaces everywhere that had
been covered by the plywood. And it bit deeply in spots.
She was ordered to grind off the glaze, in accordance
with usual shop policy, but some of the glaze went down
1/4" or more. We feared for the structural integrity
of the shelves, and told her to stop grinding. We
filled the worst pits with kiln putty, but with every
subsequent firing, the remaining glaze bit deeper.
Totally ruined.
I expect that much of the damage was due to the fact
that it wasn't really a glaze, and had none of the
viscosity that we usually demand in a glaze, to
slow it's soaking into the shelf. Many actual ash
glazes are designed to be runny, though, and it
doesn't seem impossible for a 'real' ash glaze drip
to have an effect related to the one I described.
-Snail
Tony Ferguson on tue 30 oct 01
To add to Snails post,
Yes, ash glazes do eat down into the shelf (I know)--they are among the
hardest if not the HARDEST to grind as well. AS snail said, you can pretty
much kiss your shelf good bye (save it for raku). If you are using ash
glazes, make sure (of course) that you have wash on the shelves--wadding
won't do it.
Tony Ferguson
----- Original Message -----
From: "Snail Scott"
To:
Sent: Tuesday, October 30, 2001 9:41 AM
Subject: Re: eating shelves
> At 05:18 AM 10/30/01 -0600, Mel wrote:
> >i do not think the [ash] glaze is eating into your shelf.
> >it is stuck tight, and when you pull off the pot
> >some of the shelf comes with it.
> >
>
>
> When I was a studio assistant in college, a student
> built a sculptural project, then discovered it was
> too fragile to move. So, she loaded it into the kiln
> still on its plywood board. She also put sand under
> the board. Apparently she had seen people do that
> (to reduce friction with the shelf,) but hadn't
> understood why. She then fired to ^10. No one knew
> 'til afterward.
>
> Apparently the wood ash fluxed the silica sand.
>
> The shelves (three 13"x26" mullite ones) were lightly
> glazed across their surfaces everywhere that had
> been covered by the plywood. And it bit deeply in spots.
> She was ordered to grind off the glaze, in accordance
> with usual shop policy, but some of the glaze went down
> 1/4" or more. We feared for the structural integrity
> of the shelves, and told her to stop grinding. We
> filled the worst pits with kiln putty, but with every
> subsequent firing, the remaining glaze bit deeper.
> Totally ruined.
>
> I expect that much of the damage was due to the fact
> that it wasn't really a glaze, and had none of the
> viscosity that we usually demand in a glaze, to
> slow it's soaking into the shelf. Many actual ash
> glazes are designed to be runny, though, and it
> doesn't seem impossible for a 'real' ash glaze drip
> to have an effect related to the one I described.
>
> -Snail
>
>
____________________________________________________________________________
__
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>
> 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
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_________________________________________________________
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Ababi on wed 31 oct 01
This story you tell here Snail is really important. I can suggest here
one thing.
Follow the way of Crystalline firing and put small trays under the
wares you fire with ash glaze
Ababi
>When I was a studio assistant in college, a student
>built a sculptural project, then discovered it was
>too fragile to move. So, she loaded it into the kiln
>still on its plywood board. She also put sand under
>the board. Apparently she had seen people do that
>(to reduce friction with the shelf,) but hadn't
>understood why. She then fired to ^10. No one knew
>'til afterward.
>Apparently the wood ash fluxed the silica sand.
>The shelves (three 13"x26" mullite ones) were lightly
>glazed across their surfaces everywhere that had
>been covered by the plywood. And it bit deeply in spots.
>She was ordered to grind off the glaze, in accordance
>with usual shop policy, but some of the glaze went down
>1/4" or more. We feared for the structural integrity
>of the shelves, and told her to stop grinding. We
>filled the worst pits with kiln putty, but with every
>subsequent firing, the remaining glaze bit deeper.
>Totally ruined.
>I expect that much of the damage was due to the fact
>that it wasn't really a glaze, and had none of the
>viscosity that we usually demand in a glaze, to
>slow it's soaking into the shelf. Many actual ash
>glazes are designed to be runny, though, and it
>doesn't seem impossible for a 'real' ash glaze drip
>to have an effect related to the one I described.
> -Snail
Richard Aerni on wed 31 oct 01
Tony,
Yes, I would agree that ash glaze eats into shelves...but not to the shelf's
ultimate destruction. They just don't continue to melt away (like a runaway
reactor core heading to the center of the earth), at least in my experience.
I've been firing with ash glazes, almost exclusively, for longer than twenty
years. Lots of extra runs and spills and such...and still using many of the
same shelves after 15 or more years. AND, I don't use kiln wash. No matter
how adhesive kiln wash on shelves is, in my experience at some time it
flakes and then ends up at the bottom of your best bowl. So, my shelves
look like a war zone, or a bad Jackson Pollock painting. Lots of color
patches, lots of pits and craters. I'm a big fan of alumina
hydrate...powdered onto the shelf under a "likely", mixed into my wax that
goes on the bottom of the pots, to roll my wadding balls (just extra clay
from the studio) in before placing under pot bottoms much like salt or wood
firing. Don't have many "stickers" any more. Of course, loading the kiln
takes a bit longer, but it's the results that count, right?
Richard Aerni
Bloomfield, NY
----- Original Message -----
From: "Tony Ferguson"
To:
Sent: Tuesday, October 30, 2001 7:45 PM
Subject: Re: eating shelves
> To add to Snails post,
>
> Yes, ash glazes do eat down into the shelf (I know)--they are among the
> hardest if not the HARDEST to grind as well. AS snail said, you can
pretty
> much kiss your shelf good bye (save it for raku). If you are using ash
> glazes, make sure (of course) that you have wash on the shelves--wadding
> won't do it.
>
> Tony Ferguson
>
>
> ----- Original Message -----
> From: "Snail Scott"
> To:
> Sent: Tuesday, October 30, 2001 9:41 AM
> Subject: Re: eating shelves
>
>
> > At 05:18 AM 10/30/01 -0600, Mel wrote:
> > >i do not think the [ash] glaze is eating into your shelf.
> > >it is stuck tight, and when you pull off the pot
> > >some of the shelf comes with it.
> > >
> >
> >
> > When I was a studio assistant in college, a student
> > built a sculptural project, then discovered it was
> > too fragile to move. So, she loaded it into the kiln
> > still on its plywood board. She also put sand under
> > the board. Apparently she had seen people do that
> > (to reduce friction with the shelf,) but hadn't
> > understood why. She then fired to ^10. No one knew
> > 'til afterward.
> >
> > Apparently the wood ash fluxed the silica sand.
> >
> > The shelves (three 13"x26" mullite ones) were lightly
> > glazed across their surfaces everywhere that had
> > been covered by the plywood. And it bit deeply in spots.
> > She was ordered to grind off the glaze, in accordance
> > with usual shop policy, but some of the glaze went down
> > 1/4" or more. We feared for the structural integrity
> > of the shelves, and told her to stop grinding. We
> > filled the worst pits with kiln putty, but with every
> > subsequent firing, the remaining glaze bit deeper.
> > Totally ruined.
> >
> > I expect that much of the damage was due to the fact
> > that it wasn't really a glaze, and had none of the
> > viscosity that we usually demand in a glaze, to
> > slow it's soaking into the shelf. Many actual ash
> > glazes are designed to be runny, though, and it
> > doesn't seem impossible for a 'real' ash glaze drip
> > to have an effect related to the one I described.
> >
> > -Snail
> >
> >
>
____________________________________________________________________________
> __
> > 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.
>
>
> _________________________________________________________
> Do You Yahoo!?
> Get your free @yahoo.com address at http://mail.yahoo.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 Baymore on wed 31 oct 01
Hi.
I think it depends a LOT on the type of shelf you are talking about.
Mayor mel might be talking more about silicon carbide shelves. In my
experience also the ash just kinda' sits mostly on the surface....easy to=
grind. Shelf of choice for the wood kiln. Costs lots....... lasts long.=
=
Good economy. Spend now ........ save later. I've got 20 years in a woo=
d
kiln on some of my Norton (now Saint Globain) silicon carbide shelves.
With other types of shelves (high alumina, mullite, etc) my experience sa=
ys
that the open porous structure of the shelf seems to allow the heavy ash
runs to penetrate down into the structure. A bad run can go pretty deep.=
=
Can be a real pain to clean up. Pretty much trashes the shelf. Worst
one's in this regard I have found are the shelves from Thorley (Ca). Suc=
h
up ash runs like a sponge.
As Tony says..... if you use ash glazes ..... and you don't really KNOW t=
he
glaze.... or have GOOD control of the kiln............put cookies or wads=
under the peices. Beats the heck out of "plastering" an expensive
shelf.....and also ruining a saleable pot.
Yes.... it's a pain in the butt! Welcome to the world of the woodfire=
r
. Cookies and wads everywhere. When I fire the noborigama it takes
about 200 lbs of wet mixture for the cookies alone. (In that case it is
mostly for the fly ash issues.). My shard pit is FULL of old cookies. =
Chocolate chip is my favorite .
Best,
..............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JohnBaymore.com
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"=
=
John and Dorothy Weber on thu 1 nov 01
John/Richard/Tony/Snail and Mel and all
I think you have convinced us to buy the silicon carbide shelves. We have
our share of "parts of shelves". Tell me about the cookies. Are they just a
slab of wet clay placed under each piece and then fired up, not bisquit
first ?
We are pretty good at determining which pot is a likely candidate to run,
due to shape and glaze application. I have now changed my way of spraying
and we have increased the temp to cone 11 with very good results. So all in
all our disasters are far far fewer than in the beginning but they do
sometimes occur.
We have found through this life long learning process, that the greater time
spent on the front end of the process certainly produces better results in
the end.
Looking forward to your thoughts.
Dorothy Weber
Manakin-Sabot, Va.
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of John Baymore
Sent: Wednesday, October 31, 2001 11:08 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: eating shelves
Hi.
I think it depends a LOT on the type of shelf you are talking about.
Mayor mel might be talking more about silicon carbide shelves. In my
experience also the ash just kinda' sits mostly on the surface....easy to
grind. Shelf of choice for the wood kiln. Costs lots....... lasts long.
Good economy. Spend now ........ save later. I've got 20 years in a wood
kiln on some of my Norton (now Saint Globain) silicon carbide shelves.
With other types of shelves (high alumina, mullite, etc) my experience says
that the open porous structure of the shelf seems to allow the heavy ash
runs to penetrate down into the structure. A bad run can go pretty deep.
Can be a real pain to clean up. Pretty much trashes the shelf. Worst
one's in this regard I have found are the shelves from Thorley (Ca). Such
up ash runs like a sponge.
As Tony says..... if you use ash glazes ..... and you don't really KNOW the
glaze.... or have GOOD control of the kiln............put cookies or wads
under the peices. Beats the heck out of "plastering" an expensive
shelf.....and also ruining a saleable pot.
Yes.... it's a pain in the butt! Welcome to the world of the woodfirer
. Cookies and wads everywhere. When I fire the noborigama it takes
about 200 lbs of wet mixture for the cookies alone. (In that case it is
mostly for the fly ash issues.). My shard pit is FULL of old cookies.
Chocolate chip is my favorite .
Best,
..............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JohnBaymore.com
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"
____________________________________________________________________________
__
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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