Stephani Stephenson on tue 7 jan 03
Some random thoughts
When you work with wet clay , it seems to me you are already at odds
with the way commercial tile is made. It is dust pressed, where water
content is already low, where shrinkage is low, where an immense amount
of science goes into the fabrication and testing of tile with regard to
water absorption. breaking strength , abrasive hardness, non destructive
tests and destructive tests.
If you want to be completely boggled and even fascinated, get a copy of
the "American National Standard Specifications for Ceramic Tile" from
the Tile Council of America, Inc. I understand that TCI is reaching out
to studio tilemakers, making testing available to them at lower
costs.But it is certainly educational to read how tile is tested. And
interesting to know how much you do not know!
So you read that material, then you decide, where am I in relation to
this?
If you are RAM pressing with wet clay, I recommend that you talk with
your supplier with regard to their pressing bodies and the qualities you
desire. Pressing or not, your supplier should have recommendations with
regard to custom bodies. If you work with your supplier on a custom
body, you generally need to order one ton at a time. If you are hand
pressing or rolling tile, I would look for similar qualities that you
look for in a pressing, raku or sculpture bodies. I tend to favor
the pressing and raku bodies. Even some of the sculpture bodies, white
and red, especially the lowfire ones, are awful... they warp.. I don't
like them... they are too slick and fine, don't join well, crack,
warp....
A large factor will be grog. You need a well grogged body ,with a few
different sizes of grog, not just one type/size of grog in the body. You
need this to minimize shrinkage and warping, yet you don't want a body
that is too open, or it will be too porous. A dense vitrified body is
nice, but there are also other variables.
Then there are cosmetic considerations that have to do with the look of
your tile and how the grog affects it. For lower fired bodies, frit is
often added to the clay to assist with fusion at lower temps. Everything
else depends on your firing temperature , color choices, and glaze fit.
I think you need to fire to cone 04 at the absolute minimum. Problems
with lower fired bodies will tend to be with regard to porosity and
surface durability. problems with higher fired bodies will be with
shrinkage and warping. I usually fire to cone 03 - 02, at the low end.
I don't recommend my tile for exterior applications in northern
climates, but the tile is fine for non freezing water environments.
Many tilemakers work at cone 5-6, which puts you into a better temp
range for northern climes..
Wall tile doesn't have to be entirely vitrified, in fact I think the
TCI standard for glazed Wall tile is 20% for water absorption... very
high. mine is 4%. I had one clay which I liked for color, but the
absorption was 12% which seemed very porous to me. Standard for Quarry
tile is 5%.
But look at the softness and porosity of Saltillo tile... very soft,
very porous, still useful in certain applications, so it depends on your
vision of how your tile will be used. Post firing sealants are often an
important component.
I think the overall goal for the studio artist is to find a good
balanced clay which handles well..
I look for
1. minimum problems with warping , cracking at the thickness you work
with (some work thin some work thick)
3. good working and surface characteristics (do you carve? press? hand
build? join?)
4. good color response and fit/ interaction with glazes you use. good
unglazed color, no problems with cracking warping in firing.
5. tile should 'ring' when fired.
I just hate fussy clay. A tile body doesn't have to be a special body
just a good one. An example: I was completely impressed by mel's
homemade, scrap cone 10 clay... fired to cone 10--11 . no warping on
drying and firing when used for tile....which shows that a good throwing
body can also useful as a tile body. so who knows?
I know this is very generalized info... info that Joanne , you already
know. Many of the commercial/studio tilemakers I know don't share their
clay body formulae. they work it out with their suppliers.
Interestingly, professional tilemakers are great ,warm ,open people
but a 'competitive' (yet supportive) business ethic rather than a
wide open, give it away, share it all 'collegiate' ethic seems to
pervade. This is so with glazes also. this is my observation only.
It would be nice to hear from a supplier on this topic of clay for tile.
sincerely
Stephani Stephenson
steph@alchemiestudio.com
Websites for Tile Council of America
The Tile Council of America Partnership at Clemson U.
Tile Council of America, Inc.
The Tile Council of America Partnership at Clemson University
PARTNERS
The Tile Council of America
Clemson University
American Brick Industry Companies
PARTNERSHIP PURPOSE
To partner in providing research and training to the ceramic industry of
the United States.
TYPE OF PARTNERSHIP
Research Initiatives
Contract Training/Education
DESCRIPTION
In 1996,
Clemson University, the Tile Council of America, and a large number of
American
brick industry companies constructed adjacent facilities in the Clemson
Research
Park to partner in providing research and training to the ceramic
industry of
the United
States.
The Clemson
University Ceramic Research Laboratory is 25,000 square feet,
including a
high bay area for two pilot scale manufacturing lines, one for brick
products and
one for ceramic tile. The Tile Council of America building, also about
25,000
square feet, is an administrative facility shared by the Tile Council
and
Clemson
University’s Center for Engineering Ceramic Manufacturing. The Tile
Council has
designated space in Clemson’s Ceramic Research Laboratory Building
and the full
use of the pilot scale manufacturing facility, while Clemson’s Ceramic
Center
faculty and staff have designated space in the Tile Council building.
The Tile
Council,
which relocated its national headquarters from Princeton, NJ, to
Clemson,
works
closely with the Ceramic Center faculty on a daily basis, through shared
vision
and common
objectives.
The ceramic
tile and brick industries are sharing resources and achieving common
goals at
Clemson University.
Jon Pacini on thu 9 jan 03
Stephani Stephenson wrote----------
"One white clay I have used is Laguna's WSO,
I like the way it handles. It seems to be fine bodied, but with
adequate grog for tile and sculpture purposes--(clip)--
Jon Pacini are you there? 'what up' with WSO? Would like to know more
about it."
Greetings All--Hi Stephani-- I'm present and accounted for.
Shrinkage on WSO is 12% and the absorption is 2.6% @ ^10 with moderate
reduction. WSO is one of the family of WS 4,5,10 and Big White. It fits
between WS 10 which is similar in texture but with a little less absorption,
and Big White which is similar in absorption but courser in texture.
Cracking and warping during drying is the first hurdle when making tile,
particularly larger tile. Smooth clays are susceptible to crack and warp
more than course ones during drying. If you choose a very plastic throwing
clay with a lot of shrinkage, that can be a factor in warping and cracking.
If your clay sticks to the surface its drying on or dries unevenly that can
be associated with drying cracks and warpage.
I prefer courser stoneware bodies for hand made tiles, they will
usually get you over the drying problems.That said, lots of potters use
porcelain for tiles very successfully. If you learn to work with your clay
body and understand what kind of torture you can put it through, and more
importantly what you can't, you can get nearly any clay work for you, even
porcelain.
Stephani mentioned Raku clays as being good for tile and this can be true
for a couple of reasons. First because raku clays are usually course and
secondly because they have good thermal shock characteristics.
Mullite/Kyanite and pyraxx/pyrophyllite can be found in the better Raku
bodies for their favorable thermal expansion characteristics, and they help
tile bodies for much the same reason. A large flat tile tends to heat and
cool unevenly under the best of circumstances and thermal shock will crack
an otherwise perfectly good tile. This is usually the reason tiles split in
half in the kiln.
The way tiles are stacked can have a lot to do with cracking and this is
usually a thermal shock issue. Tiles do best in a rack or with plate pins
separating and supporting them and do badly when stacked flat on top of each
other or with one edge close to the heat source.
Manufacturers mainly dry press tile, many hydraulic press moist clay or
extrude moist clay. They like smooth low fire talc bodies, for their
purposes it's a good choice. Having a talc body in a studio to me is right
there with having plaster in a studio. Sometimes it's a necessary evil but
certainly not my first choice of materials to work with.
Seems like most the potters I knew in the 70's that threw planters for a
living are now all making tile. Everything from Terra Cotta to Stoneware to
Porcelain. If you are interested in making tile, first I would suggest
getting 5 or 6 books on the subject and check out all that can be and is
being done with tile. "Handmade Tiles" by Frank Georgini is excellent,
"American Art Tile" by Norman Karlson is a great historical survey. "Ceramic
Tile for the Home", by DeBorah Goletz has some good contemporary tile and
good tips. If you really want to get carried away, try Peter King's book,
"Architectural Ceramics for the Studio Potter".
I've developed a fair amount of tile bodies for manufacturers and
studios, if I can help out, drop me a line or give me a call-------------
Jon Pacini
Clay Manager
Laguna Clay Co
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