Darrell Kimball on tue 20 feb 07
Greetings. I need your good advice. I have been following the
thread on Advancer shelves and was interested in the post about
problems with porcelain "plucking". I assume this is same thing as
"dunting?" I fire a Geil 12' brick kiln and use Advancer shelves
except on the kiln floor. Fire to cone 10 unless I misread the
cones! then it might be a half cone higher or lower. Use medium to
heavy reduction and mostly celadon and copper red glazes.
Last couple of years I've been trying to develop some skill with
porcelain and am throwing Coleman's from Ardvark. I have had quite a
bit of dunting, and have tried the following without too much
success: (1) improving the trim to eliminate any sharp edges on the
foot, either by no trim or by rounding and compressing with a metal
rib; (2) dusting the shelves with aluminum hydrate via advice from
Elaine Coleman.
I'd like to try the wadding mix with sawdust to see if that will
improve things. Question: if I make the slab type suggested and cut
it into appropriate shapes for my pots, should I bisque fire it
before the glaze firing? If I do, will the sawdust firing out be OK
in an electric kiln? I bisque to cone 05 or 06.
I thought I might try extruding the wadding mix to speed up the
process. Creating coils, starbursts, balls, etc.
Once used in a glaze firing, can the wadding be used again? or does
it lose the shrinkage benefit to help avoid cracking flat work? The
last big platter I fired using this clay, the rim cracked and totally
fell off the pot. I had used silica sand underneath and it was on
the bottom non-Advancer shelf. More likely it was my throwing and
drying, I imagine.
Sorry this post is so long, but trying to get out the facts, so maybe
someone will be able to suggest best way to solve this. Thanks a
bunch in Advance (no pun intended). Joyce K.
Hank Murrow on tue 20 feb 07
On Feb 20, 2007, at 8:06 AM, Darrell Kimball wrote:
> Greetings. I need your good advice. I have been following the
> thread on Advancer shelves and was interested in the post about
> problems with porcelain "plucking". I assume this is same thing as
> "dunting?"
Dear Darrell;
Minor quibble, but in the interest of clear communication.......
'Dunting' is cracking of the piece during cooling or rapid heating,
while 'plucking' refers to the annoying sticking of porcelain bodies to
the kiln shelf. Advancers are prone to this because the surface of the
shelf is actually a very thin 'glaze' imparted during firing of the
shelf at the factory. This 'glaze' prevents the oxidation of the SiC.
That said, I have almost eliminated the plucking with the use of
semi-coarse (60_80 mesh) alumina powder spread on the shelves, and 100
mesh alumina in my wax.
Cheers and Good Luck!
Hank in Eugene
www.murrow.biz/hank
Ron Roy on thu 22 feb 07
Porcelain is more prone to plucking - I use alumina hydrate in wax and
apply a bead on the bottom of each foot. I have not had any problems since
I started doing that.
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Snail Scott on thu 22 feb 07
At 10:06 AM 2/20/2007 -0600, you wrote:
>...was interested in the post about
>problems with porcelain "plucking". I assume this is same thing as
>"dunting?"
'Plucking' is the tendency of very vitrified clay
to stick to shelves, and leave bits behind. It is
most common with porcelain, due to its high level
of vitrification. Alumina applied lightly on the
shelf, a high-alumina kiln wash, or alumina mixed
into wax applied to the foot of the piece are
common cures.
'Dunting' is the tendency of work to crack during or
after cooling, usually a vertical crack with sharp
edges. Fast cooling and certain clays can exacerbate
the tendency.
Sounds like you've got plucking, but not dunting.
They are unrelated conditions.
-Snail
Darrell Kimball on thu 22 feb 07
Thanks for the responses to my post. Especially for correcting my
terminology. Sent me in search of the terms in my various clay books
and could not find a single reference to "plucking". The porcelain
is not always stuck to the shelves, sometimes it just starts to flake
off in little sharp splinters when I buff off a rough spot on a flap
wheel. Of course, it is always the pot you are in love with! I use
a commercial wax on bottoms prior to glazing, I assume I can mix some
alumina into that?
A peculiarity of our e-mail is that my husband's name shows up in
"From". He is my computer guru, but my name is "Joyce." Minor
issue. Thanks again for help.
Joyce K. potting away in good old Sedalia, MO
Hank Murrow on thu 22 feb 07
On Feb 22, 2007, at 5:42 AM, Darrell Kimball wrote:
> Thanks for the responses to my post. Especially for correcting my
> terminology. Sent me in search of the terms in my various clay books
> and could not find a single reference to "plucking".
Not to worry, Joyce, as most of the problems cited have been occurring
with Advancers, which have been on the market only about ten years. No
surprise that the problem hasn't reached the reference texts.
> I use a commercial wax on bottoms prior to glazing, I assume I can
> mix some alumina into that?
I assume you mean latex-type waxes? I add alumina to my "Wax that
Works"......... an improved latex wax.
Cheers, Hank
www.murrow.biz/hank
Victoria E. Hamilton on thu 22 feb 07
Ron -
What is the proportion of alumina hydrate to wax?
By "apply a bead on the bottom of each foot" do you mean several drops thick
enough to keep the whole piece up off the shelf, or is the entire foot
thickly coated?
We use a mixture of wax and alumina hydrate, but still are experiencing some
plucking.
Thanks.
Vicki Hamilton
Millennia Antica Pottery
Seattle, WA
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Wednesday, February 21, 2007 10:13 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: [CLAYART] Advancer shelves and dunting
Porcelain is more prone to plucking - I use alumina hydrate in wax and apply
a bead on the bottom of each foot. I have not had any problems since I
started doing that.
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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William & Susan Schran User on thu 22 feb 07
On 2/22/07 11:32 AM, "Hank Murrow" wrote:
> I add alumina to my "Wax that
> Works"......... an improved latex wax.
Is this a commercially available product that you have doctored?
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Carl Finch on thu 22 feb 07
At 05:42 AM 2/22/2007, Darrell (really Joyce) Kimball wrote:
>A peculiarity of our e-mail is that my husband's name shows up in
>"From". He is my computer guru, but my name is "Joyce." Minor
>issue.
And easily fixed. Since you're using Eudora (call me psychic!)
navigate as follows:
Tools/ Options/ Getting Started/ Real name:
...and type in anything you wish, such as (but no quotes),
"Joyce and her so-called Guru"
;-)
--Carl
in Medford, Oregon,
under 5" of white stuff and it's still falling,
and Pacific Power cuts the juice every few minutes.
Hank Murrow on thu 22 feb 07
On Feb 22, 2007, at 12:41 PM, William & Susan Schran User wrote:
> On 2/22/07 11:32 AM, "Hank Murrow" wrote:
>
>> I add alumina to my "Wax that
>> Works"......... an improved latex wax.
>
> Is this a commercially available product that you have doctored?
No, William, it is a wax I got from Doug Hively in Monmouth OR. He can
be reached @ Hively Pottery, 13005 S. Pacific Hwy W, Monmouth, OR
97361. It works better than anything I have tried. 503-838-6751.
LATE FLASH! Doug seems to have sold his business to Dawn Clarke, who
is at 1100 Industrial Parkway, suite B400, Newberg, OR. Try
503-537-0302.
Cheers, Hank
www.murrow.biz/hank
Snail Scott on fri 23 feb 07
At 07:42 AM 2/22/2007 -0600, you wrote:
>...I use
>a commercial wax on bottoms prior to glazing, I assume I can mix some
>alumina into that?
Yep. Just a pinch (in a yogurt-cup amount of
wax) will be enough to leave a sufficient
alumina residue after the wax burns off in
firing. If you still get plucking, add more
alumina to the wax, not more wax to the pot.
-Snail
Hank Murrow on sat 24 feb 07
On Feb 22, 2007, at 12:41 PM, William & Susan Schran User wrote:
> On 2/22/07 11:32 AM, "Hank Murrow" wrote:
>
>> I add alumina to my "Wax that
>> Works"......... an improved latex wax.
>
> Is this a commercially available product that you have doctored?
No, William, it is a wax I get from Doug Hively in Monmouth OR. He can
be reached @ Hively Pottery, 13005 S. Pacific Hwy W, Monmouth, OR
97361. It works better than anything I have tried. 503-838-6751.
>
>
> --
> William "Bill" Schran
> wschran@cox.net
> wschran@nvcc.edu
> http://www.creativecreekartisans.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.
>
>
www.murrow.biz/hank
Hank Murrow on sat 24 feb 07
On Feb 22, 2007, at 5:42 AM, Darrell Kimball wrote:
> Thanks for the responses to my post. Especially for correcting my
> terminology. Sent me in search of the terms in my various clay books
> and could not find a single reference to "plucking".
Not to worry, Joyce, as most of the problems cited have been recent
reports of the phenomena happening with Advancers which have been on
the market only about ten years.
> I use
> a commercial wax on bottoms prior to glazing, I assume I can mix some
> alumina into that?
>
> A peculiarity of our e-mail is that my husband's name shows up in
> "From". He is my computer guru, but my name is "Joyce." Minor
> issue. Thanks again for help.
>
> Joyce K. potting away in good old Sedalia, MO
>
> _______________________________________________________________________
> _______
> 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.
>
>
www.murrow.biz/hank
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