Talbott on fri 16 may 97
I recently heard someone mention that "slip cast" porcelain pottery was
less durable than similar porcelain or stoneware pottery that was thrown
from "real clay". Is there any truth to that statement that the "slip"
used to form pottery is not as durable? Does "slip" contain any grog? If
not then perhaps that accounts for its low durability. Is there also such
a thing as "stoneware slip"? Obviously I have little knowledge of slipcast
materials and techniques. Looking forward to getting "FLAMED" on this
one!!!! ....Marshall
1ST ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1997)
http://fmc.utm.edu/~dmcbeth/cag/naples.htm
Celia & Marshall Talbott, Pottery By Celia, Route 114, P O Box 4116,
Naples, Maine 04055-4116,(207)693-6100 voice and fax,(call first)
WBS Live Chat Room, Sat Nites 10 PM EDT, Private Room: Clayarters
Jonathan Kaplan on sat 17 may 97
>----------------------------Original message----------------------------
>I recently heard someone mention that "slip cast" porcelain pottery was
>less durable than similar porcelain or stoneware pottery that was thrown
>from "real clay". Is there any truth to that statement that the "slip"
>used to form pottery is not as durable? Does "slip" contain any grog? If
>not then perhaps that accounts for its low durability. Is there also such
>a thing as "stoneware slip"? Obviously I have little knowledge of slipcast
>materials and techniques. Looking forward to getting "FLAMED" on this
>one!!!! ....Marshall
>
>
So Marshall, looking to get flamed? Not from me, but I'll just give you
some straight dope.
You can manke a casting slip to fire at almost any temperature in any
atmosphere. There is no truth, absolutely no truth, to cast ware beign
less durable. In fact, I would submit that due to the nature of the
particle alignment in the casting process, slip cast ware is even stronger
and more durable than thrown ware, providing the slips have been correctly
formulated and the glaze fit is perfect. Check out Lawrence's "Ceramic
Science for the Potter" and the section on particle alignment via the
various forming methods.
I have seen and used slips that have grog in them, albeit very fine grog
that acts more like 200 mesh flint than "grog." In general, you can't
defloculate grog as it does not take an electrical charge. There also may
be an adverse effect upon the mold surface.
I have used low temperature slips. earthenware and terra cotta at cone
06-04, mid range slips at cone 3-6, and high fired stoneware and porcelain
slips at cone 9-11. All are extremely durable, exhibit low porousity and
proper glaze fit, and all in all, are a real pleasure to use. It is having
the correct information that contributes to understanding how and why
things work.
Its a matter of understanding your materials, deciding on what you want
these materials to do for you, having the important CORRECT information,
and finally, deciding if the process is one that provides you with the the
involvement you wish, the pots you wish to produce, and it if appeals to
you as a potter (comments are mine)
There are many informative texts and articles out there that can provide
you with the CORRECT information and guidance.
Jonathan
Jonathan Kaplan jonathan@csn.net
Ceramic Design Group Ltd./Production Services
PO Box 775112
Steamboat Springs CO 80477
(970) 879-9139*voice and fax
http://www.craftweb.com/org/jkaplan/cdg.shtml
http://digitalfire.com/education/articles/kaplan1.htm
Jonathan Kaplan on sat 17 may 97
I forgot to add, what is this real clay thing?? Come on, clay is clay
weather it is prepared as a polymer clay, deflocculated as a casting body,
blended as a plastic body, pressed as a non plastic tile body or extruded
as firebrick. Real clay? Whats next....real potters?
Jonathan
Jonathan Kaplan jonathan@csn.net
Ceramic Design Group Ltd./Production Services
PO Box 775112
Steamboat Springs CO 80477
(970) 879-9139*voice and fax
http://www.craftweb.com/org/jkaplan/cdg.shtml
http://digitalfire.com/education/articles/kaplan1.htm
Tony Hansen on sat 17 may 97
Talbott wrote:
> I recently heard someone mention that "slip cast" porcelain pottery was
> less durable than similar porcelain or stoneware pottery that was thrown
> from "real clay". Is there any truth to that statement that the "slip"
> used to form pottery is not as durable?
Slip ware has the potential of being much stronger. For a body to be
plastic its
recipe demands plenty of clay, whether kaolin, ball clay, stoneware
clay, bentonite,
etc. This leaves less room for flint and flux and other special purpose
minerials
(i.e. pyrophyllite, kyanite). Clays are often the dirtiest of
ceramic materials so there is reason to minimize clay content or use
less plastic cleaner clays to get good fired whiteness. Casting bodies
can be made with almost no clay content and with much cleaner lower
plastic
clays. Slip recipes are thus very adjustable and present many more
options
than plastic recipes. Because slip bodies are cleaner they tend to melt
rather
than bloat if overfired. This means they can generally be fired more
vitreous and thus much stronger. Also, it is not unusual to have 1%
drying shrinkage
in slip ware compared to 6% or more for plastic clays.
However low fire casting slip is a mix of ball clay and talc and is
used for its high expansion and tremendous working and drying
properties.
Even though it fires weak and porous, it is white and no one seems to
notice.
--
=================================================================
Tony Hansen, IMC thansen@mlc.awinc.com
INSIGHT5/Magic of Fire II demos at www.ceramicsoftware.com
Kirk Morrison on sat 17 may 97
On 16 May 97 at 7:57, Talbott wrote:
> ----------------------------Original message----------------------------
> I recently heard someone mention that "slip cast" porcelain pottery was
> less durable than similar porcelain or stoneware pottery that was thrown
> from "real clay". Is there any truth to that statement that the "slip"
> used to form pottery is not as durable? Does "slip" contain any grog? If
> not then perhaps that accounts for its low durability. Is there also such
> a thing as "stoneware slip"?
Seems to me the reason it isn't quite as durable, it is almost as if
poured right and of the proper thickness is that it is not compressed
which a thrown pot is, I a functional potter and I don't care as long
as the job gets done, I would rather decorate anyway, I enjoy that part
of the craft of pottery. Stoneware slip, yep you can get it and
porcelian slip and any thing else also you can get them as low as cone
6 or as high as cone 10.
Kirk
Kirk
Support the Jayne Hitchcock HELP Fund
Lisa or Ginny on sat 17 may 97
Talbott wrote:
> I recently heard someone mention that "slip cast" porcelain pottery was
> less durable than similar porcelain or stoneware pottery Looking forward
Marshall, you probably won't get flamed, but I certainly expect to, when
I tell you that I don't consider slip cast (ie: molded) ceramics to be
Pottery. Yes, I'm a snob. And, I've never seen slipcasted ceramics that
were as strong as pottery, because they're only fired to ^04.
--
Lisa Skeen
Living Tree Pottery
Greensboro, NC
YesIAmRU?
http://www.uncg.edu/~lpskeen
Ric Swenson on sun 18 may 97
The 'simple answer'.. ..ie 25 words or less...
There are MANY types of slip. Deflocculating and suspending some clay
materials is difficult. A common type of slip for making what I call
"CERAMICS; THE WORLD'S MOST POPULAR HOBBY wares" ( piggy banks, "soup
tureens that YOU just decorate" ) are made with what can referred to as a
TALC BODY.
This is a slip which is easy to formulate, deflocculate, pour, cast, trim
and decorate, inexpensive, easy to fire, etc. ....it has a lot of talc in
it, which, even when fired properly, isn't terribly strong. It lacks the
durability of "stoneware", "Ironware", "Porcelain" "Bone China" etc. It
is more akin to ^06 terracotta, but fires white.
Hey, that's more than 25 words!!
Flame on.
Ric
>----------------------------Original message----------------------------
>I recently heard someone mention that "slip cast" porcelain pottery was
>less durable than similar porcelain or stoneware pottery that was thrown
>from "real clay". Is there any truth to that statement that the "slip"
>used to form pottery is not as durable? Does "slip" contain any grog? If
>not then perhaps that accounts for its low durability. Is there also such
>a thing as "stoneware slip"? Obviously I have little knowledge of slipcast
>materials and techniques. Looking forward to getting "FLAMED" on this
>one!!!! ....Marshall
>
> 1ST ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1997)
> http://fmc.utm.edu/~dmcbeth/cag/naples.htm
>
> Celia & Marshall Talbott, Pottery By Celia, Route 114, P O Box 4116,
> Naples, Maine 04055-4116,(207)693-6100 voice and fax,(call first)
> WBS Live Chat Room, Sat Nites 10 PM EDT, Private Room: Clayarters
Ric Swenson, Bennington College, Route 67-A, Bennington, VT 05201-6001 ph
802 442-5401 vox 262 fax 237 direct fax line 802 442-6164 or
email rswenson@bennington.edu
Karl David Knudson on sun 18 may 97
On Sat, 17 May 1997, Kirk Morrison wrote:
> Seems to me the reason it isn't quite as durable, it is almost as if
> poured right and of the proper thickness is that it is not compressed
> which a thrown pot is
Actually, as Jonathan already mentioned, a properly formualted and cast
slip body is usually under better compression than a thrown pot, and
therefore more durable. Compression is used to align the clay particles
in throwing, where as during a cast the clay particles are automatically
aligned because of the casting process. We'll use the playing card
analogy to illustrate this. Imagine a deck of cards dumped into a pile
so that cards are strewn in all directions. Throwing compression would
be similar to trying to realign all of the cards by pushing down on the
top or side of the pile. Casting however would be similar to individually
stacking each card which will generally result in a much more ordered
and denser deck of cards. Right? Casting does have one major weakness
because of its high compression which occurs at sharp corners. Because
of the parallel alignment of the clay particles in each wall, the
point where the planes intersect will be weaker and more prone to
cracking.
Another Woodfire Weekend.
Karl in Eugene, OR
Robert Kittel on sun 18 may 97
I think that the thought here stems from the idea that slip casting (hobby)
isn't really pottery in the sense that many of us know. No matter what the
method of manufacture or temperature of firing, within reason, the clay body
(and it is real clay still) can be designed to be very hard and durable.
I am sure that Mssrs. Hansen and Kaplin have and are capable of designing
slip cast bodies that are harder and more durable than most stoneware
throwing bodies that are commercially available. I have seen wares at cone
six, slip cast and pressed that were almost indestructible.
Bob
Fay & Ralph Loewenthal on sun 18 may 97
------------------
Lisa Skeen wrote:
Marshall, you probably won't get flamed, but I certainly expect to, when I
tell you that I don't consider slip cast (ie: molded) ceramics
to be Pottery. Yes, I'm a snob. And, I've never seen slipcasted ceramics
that were as strong as pottery, because they're only
fired to =5E04.
Of course you are going to get flamed. You have
demonstrated a lack of proper analysis of the process.
First of all you can slip cast form =5E08 right up to =5E10,
maybe even higher. Secondly if you make the slip
correctly it is far more plastic and easier to work with
than any other type of clay. My wife, Fay, has worked out
a method of casting sculptured slabs, and using the
various figures, bits and pieces on cast pots. This makes
unique, interesting sculptured pots. Fay decorates each
according to what she feels it needs. It allows for more
versatality, faster production and a better product. More
importantly Fay does not get bored making and
decorating the same thing over and over again. Slip cast
items can be fired virtually wet. You just have to let them
dry enough to fettle them clean. When you stick the bits
onto the pot you do not have to scratch and wet with
slurry / slip. All in all it is a easier more versatile process.
Next time try to be more informed before making such a
statement or you just pulling my leg to get a good
reaction? Ralph in a balmy PE SA
Tony Hansen on mon 19 may 97
Lisa or Ginny wrote:
> Marshall, you probably won't get flamed, but I certainly expect to, when
> I tell you that I don't consider slip cast (ie: molded) ceramics to be
> Pottery. Yes, I'm a snob. And, I've never seen slipcasted ceramics that
> were as strong as pottery, because they're only fired to ^04.
Slip cast ceramic ware is weak, true. But I've seen lots of cone
10 reduction ware that is thin or black-cored and with poor fitting
glazes that is no stronger. But remember, slip ware can be made at any
temperature. Fire ceramic cast ware to cone 02-01 and it is very strong.
--
=================================================================
Tony Hansen, IMC thansen@mlc.awinc.com
INSIGHT5/Magic of Fire II demos at www.ceramicsoftware.com
Tony Hansen on mon 19 may 97
Fay & Ralph Loewenthal wrote:
> Of course you are going to get flamed. You have
> demonstrated a lack of proper analysis of the process.
>From this I would expect to see some pretty wise words coming up.
> First of all you can slip cast form ^08 right up to ^10,
> maybe even higher.
Alumina casting bodies go to cone 30.
> Secondly if you make the slip
> correctly it is far more plastic and easier to work with
> than any other type of clay.
Proper casting bodies have almost no plasticity because the emphasis
is on permeability and dispersability. They are very brittle in the
leather hard and dry stages but often shrink less than 2%.
> Next time try to be more informed before making such a statement.
I agree.
--
=================================================================
Tony Hansen, IMC thansen@mlc.awinc.com
Fay & Ralph Loewenthal on tue 20 may 97
Tony Hansen wrote: Proper casting bodies have almost no
plasticity because the emphasis is on permeability and
dispersability. They are very brittle in the leather hard and
dry stages but often shrink less than 2%.
We have found that with our method of making casting
slip, we have far less casualties in the fettling process.
Fay can do some very exciting work using the wet cast
straight from the mould, if the slip is plastic.
Our customers also prefer the slip as it is because it is
easier to work with.
I do not want to get into an argument with Tony since
he obviously knows what he is talking about. I just feel
one can make clay to suit ones needs and not stick
rigidly to the given norms. Tony thanks for the support
and advice you always give willingly.
Always the stroppy rebel Ralph in PE SA
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