Ann Brink on fri 11 feb 05
Tony, Have you ever exposed this kiln wash to low fire glazes? As you said,
silica needs a flux to melt at lower temps. I used to use a kiln wash
recipe of half kaolin, half silica, and after a while, the surface got shiny
and glasslike, very hard to clean off, and started grabbing the feet of high
fired stuff. I theorize that there may be fuming during low glaze firing
that fluxes that kiln wash. I switched to half alumina and half kaolin 2
yrs ago, and am happy-still have a nice dull surface. What do you think of
my theory? And Lela, do you also do some lowfire glaze firing?
Ann Brink in Lompoc CA
> > Tony
wrote:______________________________________________________________________
____
> Lela: Silica melts at a very high temperature. Ain't going to be a glass
> without a flux at our temperatures. Well over 3000F to melt it, so if
you're
> firing to cone 20 something odd you may get your silica to melt. As Mel
has
> so rightly said' Get anything on this earth hot enough and it will melt".
> Silica gravel has been used for centuries in the old ground hog kilns of
the
> south for the the floor on which pots are set.
> I have used my kiln wash 50 Alumina, 25 kaolin, 25 silica for 2 decades.
> The silica is a bit of a hardener that helps you to lift the pot, wash and
> all off the shelf if a pot becomes glazed by running to the wash.
>
lela martens on fri 11 feb 05
Thank you Tony, for such a kind responce to my knot-headed mistake. Have
been kicking myself around the block.. cheers!
Best wishes from Lela
clennell on sat 12 feb 05
Sour Cherry Pottery
>>
>> I notice several postings on this topic are advocating waddings and
>> kiln washes that have Silica as an ingredient.
>> Any comments?
>> Best regards,
>> Ivor Lewis.
>> Redhill,
>> S. Australia.
>>
> .. Yes actually, since you ask, Ivor. The thought occurs, but I figured I
> was missing something.. Silica is or is very much like flint..glass. Melts,
> runs, turns very hard again upon cooling. It seems to me to be one of the
> last materials to use in a kiln wash, like purposely applying what one is
> trying to avoid. I would try it if my aim was to securely attach my pots to
> the shelf.
> Since none of those who know much more than I didn`t remark, I assumed I had
> confused something, but still would never use for anything not wanting to
> get stuck.
> Thanks ,
> Lela__________________________________________________________________________
Lela: Silica melts at a very high temperature. Ain't going to be a glass
without a flux at our temperatures. Well over 3000F to melt it, so if you're
firing to cone 20 something odd you may get your silica to melt. As Mel has
so rightly said' Get anything on this earth hot enough and it will melt".
Silica gravel has been used for centuries in the old ground hog kilns of the
south for the the floor on which pots are set.
I have used my kiln wash 50 Alumina, 25 kaolin, 25 silica for 2 decades.
The silica is a bit of a hardener that helps you to lift the pot, wash and
all off the shelf if a pot becomes glazed by running to the wash.
Lela you ought to put a tablespoon of silica in a bowl in your kiln. Bet you
a drink at the bar you won't have glass. I'm rather partial to Knob Creek
bourbon these days.
Silica sand can also be used under big pots to let them move around on a
kiln shelf.
Cheers,
Tony
Tony and Sheila Clennell
Sour Cherry Pottery
4545 King Street
Beamsville, Ontario
CANADA L0R 1B1
http://www.sourcherrypottery.com
http://www.sourcherrypottery.com/current_news/news_letter.html
lela martens on sat 12 feb 05
. What do you think of
>my theory? And Lela, do you also do some lowfire glaze firing?
>
>Ann Brink in Lompoc CA
>
>
>Hi Ann,
I instructed children`s classes where we did lowfire out of the jar glazing,
but that`s about it. That kiln was subject to various firing types.
My own is cone 6 or primitive in the barrel in the yard.
Lela
David Hendley on sat 12 feb 05
I see no point to having silica in kiln wash except that it is a cheap
filler. Alumina is the best material for kiln wash. Add enough refractory
clay to it to make it easy to apply and stick to the kiln shelf, and you
have the best kiln wash.
I use half hydrated alumina and half EPK kaolin. It is a much
better kiln wash that my former recipe which used 200 mesh silica.
David Hendley
Working hard to make sure there is no mug left behind
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
>>
>> I notice several postings on this topic are advocating waddings and
>> kiln washes that have Silica as an ingredient.
>> Any comments?
>> Best regards,
>> Ivor Lewis.
>> Redhill,
>> S. Australia.
Steve Irvine on sun 13 feb 05
For my kiln wash I use a mixture of silica, EPK and alumina hydrate. I don't measure it or anything,
just use a scoop of each. I only put a thin coat of kiln wash on new shelves. If, after numerous
cone 10 firings, the shelf develops a surface that looks like it might become sticky to pot bottoms
I sprinkle a little alumina on the area. Most of my shelves haven't been kiln washed in years. As a
result they have a nice even surface and I don't have to do any scraping, resurfacing etc.
I do remember an incident where using silica for kiln wash did lead to a problem. One of the first
year students at Sheridan was given the job of mixing up a batch of kiln wash for the big updraft
kiln there. Unfortuneatly, she made a 50/50 batch of silica and feldspar instead of silica and EPK.
After the firing the kiln was "unloaded" with a sledge hammer!
On Sat, 12 Feb 2005 18:53:53 -0600, David Hendley wrote:
>I see no point to having silica in kiln wash except that it is a cheap
>filler. Alumina is the best material for kiln wash. Add enough refractory
>clay to it to make it easy to apply and stick to the kiln shelf, and you
>have the best kiln wash.
>I use half hydrated alumina and half EPK kaolin. It is a much
>better kiln wash that my former recipe which used 200 mesh silica.
Lee Love on mon 14 feb 05
clennell wrote:
>I absolutely stay clear of alumina hydrate in the high heat zones of my kiln
>opting for a cheap highly refractory clay instead. In my kiln, alumina wads
>on porcelain will fuse to the pot effectively ruining it or alumina wash on
>kiln shelves in the hot zone is like a skating rink.
>
>
Shells filled with wadding work well here.
--
Lee in Mashiko, Japan http://mashiko.org
http://potters.blogspot.com/ WEB LOG
http://claycraft.blogspot.com/ Photos!
clennell on mon 14 feb 05
Sour Cherry Pottery
> Tony, Have you ever exposed this kiln wash to low fire glazes? As you said,
> silica needs a flux to melt at lower temps. I used to use a kiln wash
> recipe of half kaolin, half silica, and after a while, the surface got shiny
> and glasslike, very hard to clean off, and started grabbing the feet of high
> fired stuff. I theorize that there may be fuming during low glaze firing
> that fluxes that kiln wash. I switched to half alumina and half kaolin 2
> yrs ago, and am happy-still have a nice dull surface. What do you think of
> my theory? And Lela, do you also do some lowfire glaze firing?
>
> Ann Brink in Lompoc CA
>
>
Dear Ann: I don't do low fire glazes but i do almost exclusively shino with
soda ash. the soda ash fumes and has no effect on my kiln wash. You would
think if anything would flux a wash it would be fuming soda ash since it's
melting point is low.
I think you do things in a big way. 50 this and 50 that. I like your style
but that could be the problem. My wash is 50 aluminia, 25 EPK and 25 silica.
This was written up in CM many years ago by fellow Canuck Rob Tetu and I
have used it ever since.
All the best,
Tony
clennell on mon 14 feb 05
Sour Cherry Pottery
> I see no point to having silica in kiln wash except that it is a cheap
> filler. Alumina is the best material for kiln wash. Add enough refractory
> clay to it to make it easy to apply and stick to the kiln shelf, and you
> have the best kiln wash.
> I use half hydrated alumina and half EPK kaolin. It is a much
> better kiln wash that my former recipe which used 200 mesh silica.
David; the old 50:50 alumina hydrate/kaolin mixture is a favourite at
colleges and universities where the expense is unknown to the users. the
same wash is used to make wads.
Be careful when you say the best kiln wash! Best for your kiln which fires
beautifully in under 24 hours. In longer firings, free alumina fuses to well
fluxed bodies- porcelain plucking. In the hot zone of my kiln which behaves
like a longer fired kiln, alumina is not the best- it was a thorn in my side
that i couldn't find for the longest time.
I absolutely stay clear of alumina hydrate in the high heat zones of my kiln
opting for a cheap highly refractory clay instead. In my kiln, alumina wads
on porcelain will fuse to the pot effectively ruining it or alumina wash on
kiln shelves in the hot zone is like a skating rink.
What is best in your Fast Freddie was a punch from my Cassius Clay that kept
knocking me on my arse. I kept getting up and getting punched again. Clay
did say that Canuck George Chevalo was the toughest fight of his life-15
rounds.
All the best,
Tony
Tony and Sheila Clennell
Sour Cherry Pottery
4545 King Street
Beamsville, Ontario
CANADA L0R 1B1
http://www.sourcherrypottery.com
http://www.sourcherrypottery.com/current_news/news_letter.html
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