William & Susan Schran User on fri 21 aug 09
On 8/21/09 6:46 PM, "jonathan byler" wrote:
> has anyone else used the core lite shelves? they look interesting,
> especially the price. wondering how they hold up over time as opposed
> to nitirde bonded silicon carbide and the like.
I've been testing the Corelite shelves, along with other types in our gas
fired kiln at school.
I purposely washed one side and have not flipped them to test for warping.
After a couple years of ^10 firings they seem to remain flat.
They are like any cordierite/mullite/high alumina shelf, if glaze gets into
the shelf, you'll need to chisel/grind it out.
You'll be able to read more about all the types of kiln shelves when Mel
puts the finishing touches on his kiln book.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Paul Borian on fri 21 aug 09
i have 20 new "core-light" kiln shelves coming next week which is more
straight shelves than my kiln has had in many years, and i need to use them
all right away to get caught up on all the platters and such i need to fire=
.
Most of my old shelves were too warped for those kinds of pots and i fell
behind on them as a result.
i have two kiln wash recipes here but i have never actually used one of
them. The one i do use is 1/3 epk 1/3 alumina hydrate 1/3 silica. I can't
say i have any major problems with it but it does need to be applied very
thick in order to release if the glaze drips. Then a lot of it comes off th=
e
shelf.
the recipe i have not yet tried is 75% alumina hydrate and 25% epk. I fire
to cone 11.
can anyone comment on these (or other kiln wash recipes) in terms of the
advantages/disadvantages? For example, does a kiln wash really need silica?
Would one of these release better than the other?
the only advantage i can see at the moment is that the one i use currently
is cheaper.
BTW those core-light shelves are nice - a 18X24 only weighs about 17 lbs an=
d
costs $55. By contrast, the cheap chinese silicon carbides are up to $78 fo=
r
the same size, are much heavier, and tend to warp quickly and also crack
much easier - some of the ones i bought a few years ago were warped right
from the factory.
thanks,
Paul
jonathan byler on fri 21 aug 09
Paul,
I have been using about 1 scoop silica, 1 scoop epk, and 2 scoops
alumina hydrate on our high-alumina shelves in a gas reduction kiln...
not very scientific, but for the most part at cone 9-1/2 - 10, it
seems to be doing the job well in terms of staying on the shelves and
keeping all but the most heinous glaze runs from sticking to the
shelf. if you go higher temp, you might try a little more alumina yet.
I'm not sure of the advantage of using silica, in the mix, since you
could probably get a similar chemical composition with just alumina
hydrate and EPK (more epk, less alumina) probably has something to do
with the chemical state that the ingredients are in, and the way that
running glaze materials react (or don't react) to them. the alumina
in the kaolin, from my understanding, does not have quite the same
physical properties as straight up alumina hydrate... Ivor or Edouard
or one of the other more knowledgeable chemistry-types might have a
better explanation.
has anyone else used the core lite shelves? they look interesting,
especially the price. wondering how they hold up over time as opposed
to nitirde bonded silicon carbide and the like.
jon
On Aug 21, 2009, at 1:28 PM, Paul Borian wrote:
> i have 20 new "core-light" kiln shelves coming next week which is more
> straight shelves than my kiln has had in many years, and i need to
> use them
> all right away to get caught up on all the platters and such i need
> to fire.
> Most of my old shelves were too warped for those kinds of pots and i
> fell
> behind on them as a result.
>
> i have two kiln wash recipes here but i have never actually used one
> of
> them. The one i do use is 1/3 epk 1/3 alumina hydrate 1/3 silica. I
> can't
> say i have any major problems with it but it does need to be applied
> very
> thick in order to release if the glaze drips. Then a lot of it comes
> off the
> shelf.
> the recipe i have not yet tried is 75% alumina hydrate and 25% epk.
> I fire
> to cone 11.
>
> can anyone comment on these (or other kiln wash recipes) in terms of
> the
> advantages/disadvantages? For example, does a kiln wash really need
> silica?
> Would one of these release better than the other?
> the only advantage i can see at the moment is that the one i use
> currently
> is cheaper.
>
>
>
> BTW those core-light shelves are nice - a 18X24 only weighs about 17
> lbs and
> costs $55. By contrast, the cheap chinese silicon carbides are up to
> $78 for
> the same size, are much heavier, and tend to warp quickly and also
> crack
> much easier - some of the ones i bought a few years ago were warped
> right
> from the factory.
>
> thanks,
> Paul
William & Susan Schran User on fri 21 aug 09
On 8/21/09 2:28 PM, "Paul Borian" wrote:
> i have two kiln wash recipes here but i have never actually used one of
> them. The one i do use is 1/3 epk 1/3 alumina hydrate 1/3 silica. I can't
> say i have any major problems with it but it does need to be applied very
> thick in order to release if the glaze drips. Then a lot of it comes off =
the
> shelf.
> the recipe i have not yet tried is 75% alumina hydrate and 25% epk. I fir=
e
> to cone 11.
>
> can anyone comment on these (or other kiln wash recipes) in terms of the
> advantages/disadvantages? For example, does a kiln wash really need silic=
a?
> Would one of these release better than the other?
> the only advantage i can see at the moment is that the one i use currentl=
y
> is cheaper.
I've been using a kiln wash mix of 50/50 alumina/EPK with good results
firing to ^10 for years.
I'd suggest staying away from using silica in the wash primarily due to
issues when grinding the wash off.
I also suspect a glaze accident might have more of a tendency to bond to
wash containing silica.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Steve Mills on sat 22 aug 09
I would use the second one of the two; it's very close to the recipe I use =
for all types of firing including wood/salt to cone 12, which is 3 parts by=
weight Alumina Hydrate to one part straight Kaolin. It's trouble free and =
on "normal" Cordierite-Mullite shelves needing "topping up" only after thre=
e or so firings. I've been using this recipe for a VERY long time!
Steve
Bath
UK
________________________________
From: Paul Borian
To: Clayart@LSV.CERAMICS.ORG
Sent: Friday, August 21, 2009 7:28:05 PM
Subject: need kiln wash advice please
i have 20 new "core-light" kiln shelves coming next week which is more
straight shelves than my kiln has had in many years, and i need to use them
all right away to get caught up on all the platters and such i need to fire=
.
Most of my old shelves were too warped for those kinds of pots and i fell
behind on them as a result.
i have two kiln wash recipes here but i have never actually used one of
them. The one i do use is 1/3 epk 1/3 alumina hydrate 1/3 silica. I can't
say i have any major problems with it but it does need to be applied very
thick in order to release if the glaze drips. Then a lot of it comes off th=
e
shelf.
the recipe i have not yet tried is 75% alumina hydrate and 25% epk. I fire
to cone 11.
can anyone comment on these (or other kiln wash recipes) in terms of the
advantages/disadvantages? For example, does a kiln wash really need silica?
Would one of these release better than the other?
the only advantage i can see at the moment is that the one i use currently
is cheaper.
BTW those core-light shelves are nice - a 18X24 only weighs about 17 lbs an=
d
costs $55. By contrast, the cheap chinese silicon carbides are up to $78 fo=
r
the same size, are much heavier, and tend to warp quickly and also crack
much easier - some of the ones i bought a few years ago were warped right
from the factory.
thanks,
Paul
Des & Jan Howard on sat 22 aug 09
Paul
We have never used kiln wash to enable glaze drip
release. It's purpose is to prevent plucking of dense
clay bodies by allowing easy movement of the shrinking
pot. The wash will catch glaze dusting or lumps from
handling pots, (we apply from 1 to 8 glaze layers),
& provide a layer against alkali flashing.
Kiln washed setting cookies are used for porcelain
& any glazes that may tend to run.
Glaze drips are ground off.
Our recipe 95% zircon flour, 5% kaolin.
This is brushed on as a THIN WASH not a paint.
We fire Cone -10 to Cone +12.
Des
Paul Borian wrote:
> i have two kiln wash recipes here but i have never actually used one of
> them. The one i do use is 1/3 epk 1/3 alumina hydrate 1/3 silica. I can't
> say i have any major problems with it but it does need to be applied very
> thick in order to release if the glaze drips. Then a lot of it comes off =
the
> shelf.
> the recipe i have not yet tried is 75% alumina hydrate and 25% epk. I fir=
e
> to cone 11.
>
> can anyone comment on these (or other kiln wash recipes) in terms of the
> advantages/disadvantages? For example, does a kiln wash really need silic=
a?
> Would one of these release better than the other?
> the only advantage i can see at the moment is that the one i use currentl=
y
> is cheaper.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
Paul Borian on sun 23 aug 09
i bought mine through kentucky mudworks in lexington and they get them from
Resco. I had them shipped directly from Resco.
first i just bought two of them to test and did three firings to cone 11
with no problems. These shelves weigh just about 1/2 what high alumina
shelves do.
one of the reps at resco i spoke with said they have been used in
industrial factories for several years now and he told me there is one
place that fires to cone 10, going from cold to cold, in 12 hours! (that
is, 12 hours from the time they start the kiln to the time they unload it -
but i don't suggest trying that at home)
Paul
On Aug 21, 2009 7:47pm, KATHI LESUEUR wrote:
> Paul,
> Can't answer the question on kiln wash since I never use it on my
> shelves. But, I'm in need of shelves and wondered where you got these
> from. I've always used Thorley corderite shelves until Laguna bought the
> company. Thirteen of the twenty cracked in the first firing. They cracked
> in exactly the same place with the same pattern. The rest cracked within
> six months. I wasn't able to get any reimbursement until I posted on
> Clayart and the floodgates opened with similar stories. Like you, my
> shelves are old and only a few are flat enough to risk my large platters.
> I'd love to get some new ones.
> KATHI LESUEUR
> http://www.lesueurclaywork.com
> On Aug 21, 2009, at 2:28 PM, Paul Borian wrote:
> i have 20 new "core-light" kiln shelves coming next week which is more
> straight shelves than my kiln has had in many years, and i need to use
> them
> all right away to get caught up on all the platters and such i need to
> fire.
> Most of my old shelves were too warped for those kinds of pots and i fell
> behind on them as a result.
> BTW those core-light shelves are nice - a 18X24 only weighs about 17 lbs
> and
> costs $55. By contrast, the cheap chinese silicon carbides are up to $78
> for
> the same size, are much heavier, and tend to warp quickly and also crack
> much easier - some of the ones i bought a few years ago were warped right
> from the factory.
> thanks,
> Paul
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