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kiln shelf problem

updated tue 17 aug 04

 

Rod Wuetherick on sun 15 aug 04


What cone/temp are you firing to? I don't get any plucking at all on any
porcelain (including Coleman's) and I just use alumna hydrate dusted on the
bare shelf.

Best,
Rod

------------------------------------------------------------------------
Eleanor wrote:>When I remove some of the fired pots, a tiny, thin
sliver from the
footring breaks off and sticks to the shelf.<

This often occurs with vitrified porcelain on 50/50 silica/kaolin
kiln wash. I suppose the same would hold true for some stoneware
clays.
Try changing you kiln wash formula to 50/50 alumina/kaolin and see if
that resolves the issue.
Bill

Paul Herman on sun 15 aug 04


Eleanor and All,

I want to point out there is an accepted ceramic term for the sticky
foot problem. It's called 'plucking'.

Even alumina based kiln wash will cause plucking, especially if it isn't
fresh and has been fired a time or two. Alumina in the wax seems to work
well for me.

best,

Paul Herman

Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/

----------
>From: Eleanor
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: kiln shelf problem
>Date: Sun, Aug 15, 2004, 12:35 PM
>

> When I remove some of the fired pots, a tiny, thin sliver from the
> footring breaks off and sticks to the shelf.

Jeanette Harris on sun 15 aug 04


>Dear Clayart,
>
>This topic has been done to death in the Archives but I can't find a
>reference to my particular problem. I'm puzzled; I hope you can help.
>
>I'm glaze firing in a Skutt 1027KM at ^6.
>
>When I remove some of the fired pots, a tiny, thin sliver from the
>footring breaks off and sticks to the shelf.
>
>
>I am very scrupulous about waxing footrings; --snip
>

Hi, Eleanor

I've got the very same problem. I just bought some new shelves,
coated them with kiln wash, and have fired them a couple of times in
a glaze firing. The last firing was a disaster. Same thing--well
waxed foot rings; even stilted some work and the stilts fused with
the shelves. It's gotta be the kiln wash, which I bought at one of
the suppliers. The surface of the shelves have a slightly blue,
crackly texture and a slight sheen.

I've hauled out my old shelves to do a bisque firing and recoated one
of the new shelves with a new batch of kiln wash--will test to see if
the same thing happens. Somehow, I don't think it will.

Could I have been sold an incorrectly mixed batch of kiln wash?
I checked the archives for suggestions about making my own and am
thinking of doing that if this next test doesn't work.

(Firing at cone 5, electric.)
--
Jeanette Harris
in Poulsbo WA

Eleanor on sun 15 aug 04


Dear Clayart,

This topic has been done to death in the Archives but I can't find a
reference to my particular problem. I'm puzzled; I hope you can help.

I'm glaze firing in a Skutt 1027KM at ^6.

When I remove some of the fired pots, a tiny, thin sliver from the
footring breaks off and sticks to the shelf.

Before each firing I was preparing the shelves by scraping with a
chisel and a silicon carbide rub brick and applying a thin coat of
(commercial) kiln wash.

After a time I noticed a build-up of kiln wash; bits stuck to
footrings and sometimes to the pots themselves. So following
suggestions on clayart, I bought an angle grinder, got some hands-on
instructions on its use from a friend, and angle-ground all my
shelves. As a beginner at this, I wound up with clean shelves which
were ever so slightly gouged. So I applied a new coat of kiln wash
and fired. That's when the slivering began.

I am very scrupulous about waxing footrings; I use a commercial "wax
resist" (not latex) from a bottle. Most of the glazes I use stay put
and I apply the glaze to within about a sixteenth of an inch from the
bottom and clean off any glaze that gets on the wax.

Lately I tried applying a double coat of wax resist and leaving more
of the footring unglazed. I also made a bunch of thin bisque pancakes
to put under pots. Some of these pancakes are a little warped. But I
kiln wash them and I've had no slivering problem with them---they're
just a pain to use. Pots placed directly on the shelves continue to
sliver.

I don't sell my pots but I'm beginning to think they might be good
enough to sell; I would now have to classify the slivered pots as
"seconds"---very annoying.

Short of buying new shelves, what, if anything, can I do?

TIA for your good advice.

Eleanor Kohler
Centerport, NY

Earl Brunner on sun 15 aug 04


You do not say what your clay is. I have this problem with Coleman
Porcelain; just enough of the foot seems to fuse to the shelf to cause these
chips. What works very well is to add a bit of alumina hydrate to your wax.
I don't measure it, so I can't tell you how much to add. It coats the foot
rim with a fine coating of alumina powder. I keep two wax containers, one
clearly marked W/Alumina, and one without. You do not want to use the
alumina wax as regular wax resist in other applications.

Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Eleanor
Sent: Sunday, August 15, 2004 12:35 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: kiln shelf problem

Dear Clayart,

This topic has been done to death in the Archives but I can't find a
reference to my particular problem. I'm puzzled; I hope you can help.

I'm glaze firing in a Skutt 1027KM at ^6.

When I remove some of the fired pots, a tiny, thin sliver from the
footring breaks off and sticks to the shelf.

Before each firing I was preparing the shelves by scraping with a
chisel and a silicon carbide rub brick and applying a thin coat of
(commercial) kiln wash.

After a time I noticed a build-up of kiln wash; bits stuck to
footrings and sometimes to the pots themselves. So following
suggestions on clayart, I bought an angle grinder, got some hands-on
instructions on its use from a friend, and angle-ground all my
shelves. As a beginner at this, I wound up with clean shelves which
were ever so slightly gouged. So I applied a new coat of kiln wash
and fired. That's when the slivering began.

I am very scrupulous about waxing footrings; I use a commercial "wax
resist" (not latex) from a bottle. Most of the glazes I use stay put
and I apply the glaze to within about a sixteenth of an inch from the
bottom and clean off any glaze that gets on the wax.

Lately I tried applying a double coat of wax resist and leaving more
of the footring unglazed. I also made a bunch of thin bisque pancakes
to put under pots. Some of these pancakes are a little warped. But I
kiln wash them and I've had no slivering problem with them---they're
just a pain to use. Pots placed directly on the shelves continue to
sliver.

I don't sell my pots but I'm beginning to think they might be good
enough to sell; I would now have to classify the slivered pots as
"seconds"---very annoying.

Short of buying new shelves, what, if anything, can I do?

TIA for your good advice.

Eleanor Kohler
Centerport, NY

____________________________________________________________________________
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Anne Webb on sun 15 aug 04


hey eleanor..

just curious ...what clay are you using?

a couple of things.. if i understand correctly you ground all of the shelves
to the point where there was no kiln wash left, yes? then you put a coat of
kiln wash on. perhaps your initial coat of kiln wash wasnt thick enough as
the kiln wash is supposed to flake off, not your pot. (this doesnt mean
apply a thickening up your kiln wash mixture btw, just add more coats)

I too use a commercial wax resist diluted somewhat with water.. i think i do
1/3 water to 2/3 wax..makes it go farther and has nicer consistency. a
thicker wax coat wont prevent sticking to your shelf btw. i also add
alumina hydrate to the wax (enough so you can see it when you are brushing
it on the pot). The alumina acts kind of like "ball bearings" between the
pot foot and the kiln shelf and prevents sticking. Its also good for waxing
galleries/lids on pots ... makes them a little easier to seperate. I brush
the wax on with one of those little foam brushes (cheap) you get at the
hardware store.. center your pot on a banding wheel, hold the brush in place
with one hand and with the other, spin the banding wheel...nice clean line
and you can really control your application.
perhaps the alumina in your wax resist will help with your sticking.

for pots you are going to use glazes on that have a tendency to run,
sometimes it helps to make a little ridge toward the bottom of the pot when
you are throwing or trimming that will help catch the glaze. doesnt always
work but it sometimes does. also, its acceptable to have the glaze 1/8th of
an inch from the bottom of the foot of your pot vs 1/16.

anyway, would love to hear how you make out. take care..anne

>From: Eleanor
>Reply-To: Clayart
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: kiln shelf problem
>Date: Sun, 15 Aug 2004 15:35:08 -0400
>
>Dear Clayart,
>
>This topic has been done to death in the Archives but I can't find a
>reference to my particular problem. I'm puzzled; I hope you can help.
>
>I'm glaze firing in a Skutt 1027KM at ^6.
>
>When I remove some of the fired pots, a tiny, thin sliver from the
>footring breaks off and sticks to the shelf.
>
>Before each firing I was preparing the shelves by scraping with a
>chisel and a silicon carbide rub brick and applying a thin coat of
>(commercial) kiln wash.
>
>After a time I noticed a build-up of kiln wash; bits stuck to
>footrings and sometimes to the pots themselves. So following
>suggestions on clayart, I bought an angle grinder, got some hands-on
>instructions on its use from a friend, and angle-ground all my
>shelves. As a beginner at this, I wound up with clean shelves which
>were ever so slightly gouged. So I applied a new coat of kiln wash
>and fired. That's when the slivering began.
>
>I am very scrupulous about waxing footrings; I use a commercial "wax
>resist" (not latex) from a bottle. Most of the glazes I use stay put
>and I apply the glaze to within about a sixteenth of an inch from the
>bottom and clean off any glaze that gets on the wax.
>
>Lately I tried applying a double coat of wax resist and leaving more
>of the footring unglazed. I also made a bunch of thin bisque pancakes
>to put under pots. Some of these pancakes are a little warped. But I
>kiln wash them and I've had no slivering problem with them---they're
>just a pain to use. Pots placed directly on the shelves continue to
>sliver.
>
>I don't sell my pots but I'm beginning to think they might be good
>enough to sell; I would now have to classify the slivered pots as
>"seconds"---very annoying.
>
>Short of buying new shelves, what, if anything, can I do?
>
>TIA for your good advice.
>
>Eleanor Kohler
>Centerport, NY
>
>______________________________________________________________________________
>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.

_________________________________________________________________
Donít just search. Find. Check out the new MSN Search!
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william schran on sun 15 aug 04


Eleanor wrote:>When I remove some of the fired pots, a tiny, thin
sliver from the
footring breaks off and sticks to the shelf.<

This often occurs with vitrified porcelain on 50/50 silica/kaolin
kiln wash. I suppose the same would hold true for some stoneware
clays.
Try changing you kiln wash formula to 50/50 alumina/kaolin and see if
that resolves the issue.
Bill

Rare - Earth - Design on sun 15 aug 04


Eleanor,
I used to have a similar problem with a porcelain body on silicon carbide
shelves. The solution I found was to dust each shelf with calcined alumina.
I use a fine mesh flour sieve bought from a hardware store and give a light
dusting to each shelf, run my thumb around the edge on top to make sure
none will fall off onto the pots below, never had any bottoms stick since.
I fire to cone 12 in a gas kiln and have never waxed the bottom of my pots,
I have known other potters who used fine bodied stoneware have the same
problem and the firing temperatures were different, the alumina solved the
problem but some were careless in cleaning around the edges of shelves, or
sliding pots back on shelves, be careful, if some falls into a pot on a
lower
shelf you will not even make a second of it.
Regards,
Bob Hollis
----- Original Message -----
From: "Eleanor"
To:
Sent: Sunday, August 15, 2004 8:35 PM
Subject: kiln shelf problem


> Dear Clayart,
>
> This topic has been done to death in the Archives but I can't find a
> reference to my particular problem. I'm puzzled; I hope you can help.
>
> I'm glaze firing in a Skutt 1027KM at ^6.
>
> When I remove some of the fired pots, a tiny, thin sliver from the
> footring breaks off and sticks to the shelf.
>
> Before each firing I was preparing the shelves by scraping with a
> chisel and a silicon carbide rub brick and applying a thin coat of
> (commercial) kiln wash.
>

Earl Brunner on sun 15 aug 04


Even with my kiln wash recipe of 60 alumina hydrate, 30 epk and 10
bentonite, coleman porcelain still slivered without the additional alumina
in the wax.

Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of william schran
Sent: Sunday, August 15, 2004 4:35 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: kiln shelf problem

Eleanor wrote:>When I remove some of the fired pots, a tiny, thin
sliver from the
footring breaks off and sticks to the shelf.<

This often occurs with vitrified porcelain on 50/50 silica/kaolin
kiln wash. I suppose the same would hold true for some stoneware
clays.
Try changing you kiln wash formula to 50/50 alumina/kaolin and see if
that resolves the issue.
Bill