Eric Serritella on sat 23 apr 05
I've been working with a thick slip on Cone 6 porcelain and stoneware. =
Even when dried slowly, I still get some cracking and apparent loss of =
adhesion to the base form. I apply it when the pot is leather hard, and =
spritz the pot with a little water if it seems a little dry. I dry it =
under plastic as soon as it has hardened up enough to be covered. With =
the welcoming of our first child last week, I am looking for a way to =
make the slip more forgiving of interruptions, etc. as I work out of a =
home studio. Time for more experimentation is now more limited than =
before.=20
The slip recipe I use is:
OM-4 55%
Grolleg China Clay 35%
Custer Feldspar 10%
I don't want to go any lower on the Grolleg, as the glazes I'm using =
have better color on a brighter white surface. In fact I started with a =
45/45/10 recipe attributed to Phil Rogers and have since adjusted it as =
above hoping higher ball clay content would help, but it didn't.
Does anyone have experience on how to make the slip more plastic and/or =
forgiving so it will adhere better to the base pot? Will CMC, bentonite, =
VeeGum, etc. help, and in what percent? Any input/ideas would be great.
Thanks!
Eric (aka Daddy)
Muddy Paws Pottery
528 Sebring Road
Newfield, NY 14867
607.564.7810
www.muddypawspottery.com
Vince Pitelka on sun 24 apr 05
Eric wrote:
"I've been working with a thick slip on Cone 6 porcelain and stoneware. Even
when dried slowly, I still get some cracking and apparent loss of adhesion
to the base form. I apply it when the pot is leather hard, and spritz the
pot with a little water if it seems a little dry. I dry it under plastic as
soon as it has hardened up enough to be covered. With the welcoming of our
first child last week, I am looking for a way to make the slip more
forgiving of interruptions, etc. as I work out of a home studio. Time for
more experimentation is now more limited than before. The slip recipe I use
is: OM-4 55%, Grolleg China Clay 35%, Custer Feldspar 10%"
Eric -
I've done a lot of slip decoration in the past, and I maybe able to offer
some useful advice. With that much ball clay, this will be a very
high-shrinkage slip, inappropriate for application to leather-hard pots.
Generally, thick-slip techniques do not work well on leather hard clay.
They are usually done on very fresh clay, otherwise shrinkage causes the
kind of problems you are experiencing. I'd cut the ball clay down to 20%,
add 25% flint plus 3% bentonite (for adhesion), keep the feldspar at 10%,
and increase the Grolleg accordingly. Apply the slip when the clay has
stiffened only slightly. That should help. The Grolleg is not the problem,
but you have too much clay overall in this slip, and no non-plastics except
the feldspar.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Alex Solla on sun 24 apr 05
Eric-
To add to Vince's post:
Clay isnt the only culprit in shrinkage. Water adds to the mix. In short, less water = less shrinkage. So to make water wetter as they say, you need a deflocculated slip. A lot of folks use Darvan for this. Mix the slip wicked thick, thick as paste, then drop by drop add your deflocculant, at some point, it will get to the exact stage you want. Too much, and it goes sploosh. Yep, technical term. Sploosh.
Congrats on becoming a Daddy.
cheers,
Alex Solla
Cold Springs Studio
4088 Cold Springs Road
Trumansburg, NY 14886
607-387-4042 voice/fax
alexandersolla@yahoo.com
www.coldspringsstudio.com
Vince Pitelka wrote:
Eric wrote:
"I've been working with a thick slip on Cone 6 porcelain and stoneware. Even
when dried slowly, I still get some cracking and apparent loss of adhesion
to the base form. I apply it when the pot is leather hard, and spritz the
pot with a little water if it seems a little dry. I dry it under plastic as
soon as it has hardened up enough to be covered. With the welcoming of our
first child last week, I am looking for a way to make the slip more
forgiving of interruptions, etc. as I work out of a home studio. Time for
more experimentation is now more limited than before. The slip recipe I use
is: OM-4 55%, Grolleg China Clay 35%, Custer Feldspar 10%"
Eric -
I've done a lot of slip decoration in the past, and I maybe able to offer
some useful advice. With that much ball clay, this will be a very
high-shrinkage slip, inappropriate for application to leather-hard pots.
Generally, thick-slip techniques do not work well on leather hard clay.
They are usually done on very fresh clay, otherwise shrinkage causes the
kind of problems you are experiencing. I'd cut the ball clay down to 20%,
add 25% flint plus 3% bentonite (for adhesion), keep the feldspar at 10%,
and increase the Grolleg accordingly. Apply the slip when the clay has
stiffened only slightly. That should help. The Grolleg is not the problem,
but you have too much clay overall in this slip, and no non-plastics except
the feldspar.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
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John Kudlacek on mon 25 apr 05
Hi Eric,
In a recent search for a very thick slip to create textured affects on
porcelain I found that by adding Gold Bond Wallpaper Paste and Size to the
slip I discovered, much to my amazement, that the slip adhered to the
porcelain body when applied at all stages, wet, leather hard and bone dry.
It survived both bisque and cone 10 without popping off. I'll see if I
can find the recipe and send it to you. If if forget, rattle my chain.
Down side, it does not store indefinitely. Phew!
John Kudlacek
John Rodgers on mon 25 apr 05
Eric,
When I attach porcelain to porcelain, stoneware to stoneware, I make a
thick slurry of the clay I am using, and then sometimes add vinegar to
it and mix thoroughly. This will thicken it into a paste. I use this
paste to make attachments. before I apply the paste, I wet both contact
surfaces with magic water - a mix of a quart of water (I use distilled),
a table spoon of sodium silicate and a 1/2 table spoon of soda
ash.(others use more or less of the sodium silicate and soda ash). Next
I apply the paste.
An alternate method I use is to make paper clay of each of the clays I
use. Then I add enough of the magic water to make a soft paste. I use
this to patch holes, cracks, etc, as well as assembling attachments.
As long as I am on the subject of patching cracks, there are times when
I will fill a crack in bisque by using calcined clay of the same type as
the pot I'm working on mixed into a bit of the glaze I'm going to use so
as to make a paste and work it into the crack. Then I glaze it over all.
After firing, it looks great. Doesn't work 100 % of the time without
leaving a blemish, but often enough.
Hope this helps.
Regards,
John Rodgers
Chelsea, AL
Eric Serritella wrote:
>I've been working with a thick slip on Cone 6 porcelain and stoneware. Even when dried slowly, I still get some cracking and apparent loss of adhesion to the base form. I apply it when the pot is leather hard, and spritz the pot with a little water if it seems a little dry. I dry it under plastic as soon as it has hardened up enough to be covered. With the welcoming of our first child last week, I am looking for a way to make the slip more forgiving of interruptions, etc. as I work out of a home studio. Time for more experimentation is now more limited than before.
>
>The slip recipe I use is:
>OM-4 55%
>Grolleg China Clay 35%
>Custer Feldspar 10%
>
>I don't want to go any lower on the Grolleg, as the glazes I'm using have better color on a brighter white surface. In fact I started with a 45/45/10 recipe attributed to Phil Rogers and have since adjusted it as above hoping higher ball clay content would help, but it didn't.
>
>Does anyone have experience on how to make the slip more plastic and/or forgiving so it will adhere better to the base pot? Will CMC, bentonite, VeeGum, etc. help, and in what percent? Any input/ideas would be great.
>
>Thanks!
>
>Eric (aka Daddy)
>
>
>Muddy Paws Pottery
>528 Sebring Road
>Newfield, NY 14867
>607.564.7810
>www.muddypawspottery.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.
>
>
>
>
John Kudlacek on mon 25 apr 05
Hi Vince,
Having grown up in a small rural community, I can relate to your
brother's simily, "looks like it was reparied by a farmer". References
like that were frequently used by family and friends and were not often
complimentary. However, to me it implies that someone repaired it(the air
conditioner) that had no training or special skills but got the job done
by ingenuity and resourcefullness, traits common to those relying on the
land for their sustenance. The subject brings to mind and oft repeated
phrase of my father,s, "farmers can do anything". Often living in
isolation and without much in the way of financial resources, potters
resemble those "farmers" and do just about everyting.
John Kudlacek
wendy kershaw on mon 25 apr 05
Hi Eric,
Yep sounds like you've too much raw clay in your mix. One way to keep
the same amounts might be to calcine some of your high shrink
ingredients. IE. put them in a biscuit fired bowl and fire to cone 06,
this will pre-shrink them, so you should get less problems applying
your slip to raw clay. I've a reciepe for vitreous slip which does
this, and is designed to be put on biscuited ware.
Hope this makes sense!
Yours,
Wend :o)
Ron Roy on wed 27 apr 05
Hi Eric,
Calcining part of the slip will help but - as others have said - defloccing
is probably the right thing to do.
Keep track of how much dry body you add to how much slip as you add the
defloccer - I use Darvan - and how much Darvan - so when you make it up
again you will know how much of each to blend from the beginning - it's a
lot easier the 2nd time.
RR
>I've been working with a thick slip on Cone 6 porcelain and stoneware.
>Even when dried slowly, I still get some cracking and apparent loss of
>adhesion to the base form. I apply it when the pot is leather hard, and
>spritz the pot with a little water if it seems a little dry. I dry it
>under plastic as soon as it has hardened up enough to be covered. With the
>welcoming of our first child last week, I am looking for a way to make the
>slip more forgiving of interruptions, etc. as I work out of a home studio.
>Time for more experimentation is now more limited than before.
>
>The slip recipe I use is:
>OM-4 55%
>Grolleg China Clay 35%
>Custer Feldspar 10%
>
>I don't want to go any lower on the Grolleg, as the glazes I'm using have
>better color on a brighter white surface. In fact I started with a
>45/45/10 recipe attributed to Phil Rogers and have since adjusted it as
>above hoping higher ball clay content would help, but it didn't.
>
>Does anyone have experience on how to make the slip more plastic and/or
>forgiving so it will adhere better to the base pot? Will CMC, bentonite,
>VeeGum, etc. help, and in what percent? Any input/ideas would be great.
>
>Thanks!
>
>Eric (aka Daddy)
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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