Susan Cline on sun 16 oct 05
(My apologies to the moderator, and Gayle, if this message is received
2X -- seems my "reply" went directly to Gayle the first time....)
This brings to mind a problem I'm having. In a community studio where I
used to work we were required to use "clay patties" under our work or
pay a certain amount for each "drip" onto the shelves.
I got into this habit and have never used kiln wash on my own shelves.
HOWEVER, recently on almost every piece, the clay patty takes a small
chunk out of the footring of my pieces. This happens on almost every
piece, spoiling a nicely finished footring and requiring grinding. It
does not seem to matter if the clay patty is new - never before used -
or if I'm reusing one.
I am currently firing (^6 electric) a load wherein I spread some grog
on each of the clay patties, hoping for a ball bearing type of result,
in case it was some sort of uneven shrinkage causing the problem. I
don't know the result yet.
I wonder if anyone else has had this problem and if anyone has
suggestions for me.
Thank you.
Sue Cline
Cincinnati, OH
Potters' Council Member
On Oct 16, 2005, at 3:47 PM, claybair wrote:
> ".....I make/use little "wasters" and place under self supporting
> cones...
> and don't get divots in the shelves anymore...."
>
> Gayle Bair
> Bainbridge Island, WA
> Tucson, AZ
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claybair on sun 16 oct 05
I make/use little "wasters" and place under self supporting cones...
and don't get divots in the shelves anymore.
Gayle Bair
Bainbridge Island, WA
Tucson, AZ
http://claybair.com
-----Original Message-----
From: Gail Dapogny
Vince,
Re. wasters...Guess I never really thought of the meaning. All I know
is that, after years of the usual stacking, firing, unstacking,
reseaching and purchasing kiln shelves, grinding shelves, etc. etc, one
day my patience utterly snapped, and I said "We HAVE to start using
those flat clay cookies for unknown glazes, tests, and our students'
work!! We're trashing too many shelves" Someone said, "Yeah,
wasters." The term stuck. Everyone made communal "wasters" which we
use over and over.
snip>
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Daniel Semler on tue 18 oct 05
Hi Sue,
> recently on almost every piece, the clay patty takes a small
> chunk out of the footring of my pieces.
This sounds very like "plucking", where a bit of the foot gets stuck to the
shelf and breaks away from the piece when you unload it. Are you using a well
vitrified porcelain, for example ? That's where I've seen this before. The
stonewares I've used don't seem to display this problem. Anyhow, the usual fix
is a small amount of alumina in the wax applied to the foot so you get
the ball
bearing affect you describe.
I believe the reason it happens is that the clay body gets soft to the point
of bonding with the shelf or patty, hence the reason that it occurs with well
vitrified bodies.
Thanx
D
Ron Roy on wed 19 oct 05
Hi Sue,
This is silica in the cookie combining with the silica in the pot - it's
the reason there should not be silica in kiln wash.
The suggestion to include alumina in the foot wax is good but can lead to
another problem.
I use two kinds of wax - the first coat (no alumina) goes on as a glaze
resist - then I put some (with alumina) just on the bottom of the foot. If
the alumina gets under the glaze it will be a problem - the glaze will lift
and can be very sharp.
You can always kiln wash the cookies.
RR
>This brings to mind a problem I'm having. In a community studio where I
>used to work we were required to use "clay patties" under our work or
>pay a certain amount for each "drip" onto the shelves.
>
>I got into this habit and have never used kiln wash on my own shelves.
>HOWEVER, recently on almost every piece, the clay patty takes a small
>chunk out of the footring of my pieces. This happens on almost every
>piece, spoiling a nicely finished footring and requiring grinding. It
>does not seem to matter if the clay patty is new - never before used -
>or if I'm reusing one.
>
>I am currently firing (^6 electric) a load wherein I spread some grog
>on each of the clay patties, hoping for a ball bearing type of result,
>in case it was some sort of uneven shrinkage causing the problem. I
>don't know the result yet.
>
>I wonder if anyone else has had this problem and if anyone has
>suggestions for me.
>
>Thank you.
>
>Sue Cline
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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