Janet or Michael Francoeur on wed 20 aug 97
I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
thick and are 14 " hexagons and EVERY time they crack right across the
middle, if not in the bisque then in the glaze. Anyone have any ideas?
Thank you in advance
Janet Francoeur
New Bern, North Carolina
Craig Martell on wed 20 aug 97
At 12:00 AM 8/20/97 EDT, Janet wrote:
>----------------------------Original message----------------------------
>I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
>but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
>thick and are 14 " hexagons and EVERY time they crack right across the
>middle, if not in the bisque then in the glaze. Anyone have any ideas?
Hi:
What type of clay are the tiles made with? What is your bisque temp., and
what is the glaze firing temp? How are you setting the tiles in the kiln
for bisque and glaze firing? How do you judge the maturation temp in both
firings, by visual cones in the kiln, or some other means such as a
pyrometer etc. Sorry to just ask a bunch of questions but depending on the
answers, I may be able to offer some suggestions, or maybe a solution!!
regards, Craig Martell-Oregon
LINDA BLOSSOM on wed 20 aug 97
Dear Janet,
Are you firing these flat? I was going to ask if you were firing across
half shelves or one shelf. I did a large slab once that was about 24" by
23" and I fired it vertically, using hard brick behind as a support. I just
fired a shelf that I made that had a back about 20" wide and 10" tall. I
fired this flat. Neither had any problem and both were about 1/2" thick.
This was fired on a half shelf. I single fire at 100 C per hour and use a
highly grogged, high fireclay body. I would always attempt to not have a
piece cross two shelves. Never seems flat enough. Are you making these
with a slab roller?
"I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
thick and are 14 " hexagons and EVERY time they crack right across the
middle, if not in the bisque then in the glaze. Anyone have any ideas?"
Linda Blossom
2366 Slaterville Rd.
Ithaca, NY 14850
607-539-7912
blossom@lightlink.com
http://www.artscape.com
Ric Swenson on wed 20 aug 97
Janet,
Now you know why most of the tiles you see are smaller sizes.
First thing I would do is consider the clay body. Maybe open it up with
grog or mullite/Kyanite? You don't give us much info. on how you are making
these tiles....so I will proceed into "one of my rambles"....
Have made 12 X 12 X 3/8" thick porcelain tiles....thousands of them for
mural projects....like the Reading Station Mural, Phil, Pa. for Larry
Rivers and Sung Moy Mural in NYC. Even using the 120 ton RAM press, we had
cracking, warping and all sorts of problems to conquer.
Ideas to explore for your situation might include: First, a forgiving
clay body that will dry without cracking and warping excessively and fire
decently....several times....? ...(our tiles had to be fired up to four
times in progressively lower temperature firings.) Check methods of drying,
turning the tiles as they dry, and / or drying on open mesh screens.?
If you are hand rolling slabs, or using a slab roller, there may not be
enough 'compression' in your forming method?
Maybe try throwing big flat, thick plates ( use a big wood rib and
"compress the snot" out of them, as thrown ?) ....then cut them, when
cheese -hard, using a hex shaped template?
How do you stack your tiles in the kiln?...One on a shelf?.....stacked on
top of each other? ON edge? What's the firing schedule? Tiles too close
to electric elements?
Have you tried a generous coating of sand or alumina hydrate on kiln
shelves....to allow your tiles to "float" as the fire shrinks them ?
LOTS of things to consider...
You could call a kiln shelf manufacturer, like Thorley's in California.
They might be able to give you some tips....(or even sell you hexagonal
tiles! ) They cast most of their mullite shelves, as I recall. Try casting
yours?
Hope some of this is helpful.
Grist for the mill.
Ric
>----------------------------Original message----------------------------
>I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
>but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
>thick and are 14 " hexagons and EVERY time they crack right across the
>middle, if not in the bisque then in the glaze. Anyone have any ideas?
>Thank you in advance
>Janet Francoeur
>New Bern, North Carolina
############################################################################
FROM: Ric Swenson, Bennington College, Route 67-A, Bennington Vermont
05201-6001. (802) 442-5401 ext. 262 (fax ext. 237) or
fax direct to: (802) 442-6164
rswenson@bennington.edu
############################################################################
Jonathan Kaplan on wed 20 aug 97
>----------------------------Original message----------------------------
>I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
>but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
>thick and are 14 " hexagons and EVERY time they crack right across the
>middle, if not in the bisque then in the glaze. Anyone have any ideas?
>Thank you in advance
>Janet Francoeur
>New Bern, North Carolina
Tiles, because of their shape, exhibit differential heating, meaning, that
as they are thin in cross section and flat top and bottom, they absorb and
release heat differently.(greater surface area on the top and bottom than
on the edge.) As they may be fired with the large surface area in contact
with the kiln shelves, there are problems resulting from this, as well as
stacking tiles on top of each other.
Minimize the contact of the tile with the kiln shelf either by using
commercial tile setters
to hold the tiles, both in bisque and in the glaze fire. Try firing the
tiles on edge, but use spacers under the edges to minimize the contact of
the edge onto the kiln shelf. We haveused a diamond saw to cut old kiln
shelves into narrow strips to support the tile.
Of course it could be the forming technique of the compostion of the clay
body. We press tiles and have made many by slab and slip casting. It has
proven that careful firing and orientation of the tiles on the shelf (as
above) and NOT the forming process usually is the culprit in my plant.
Good luck
Jonathan
Jonathan Kaplan, president jonathan@csn.net
Ceramic Design Group Ltd./Production Services
PO Box 775112
Steamboat Springs CO 80477
Plant Location (please use this address for all UPS shipments)
30800 Moffat Ave Unit 13
Steamboat Springs CO 80487
(970) 879-9139*voice and fax
http://www.craftweb.com/org/jkaplan/cdg.shtml
http://digitalfire.com/education/clay/kaplan1.htm
Andrew & Laura Conley on wed 20 aug 97
Do your 14" hexagon tiles fit completely on one kiln shelf? If not,
could the stress of being on two shelves that are not EXACTLY the same
height be cracking them????
Janet or Michael Francoeur wrote:
>
> ----------------------------Original message----------------------------
> I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
> but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
> thick and are 14 " hexagons and EVERY time they crack right across the
> middle, if not in the bisque then in the glaze. Anyone have any ideas?
> Thank you in advance
> Janet Francoeur
> New Bern, North Carolina
stevemills on thu 21 aug 97
Janet,
could you post the composition of the clay you are using. We usually
find the most successful tile bodies contain at least 35-40% sand or
fine grog often more. With a 14" big tile you also have a lot of
stresses built in if you are rolling out or using a similar technique.
It is no accident that historically tile makers have used the very soft
"clot & frame" method to make tiles.
Steve.
In message , Janet or Michael Francoeur writes
>----------------------------Original message----------------------------
>I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
>but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
>thick and are 14 " hexagons and EVERY time they crack right across the
>middle, if not in the bisque then in the glaze. Anyone have any ideas?
>Thank you in advance
>Janet Francoeur
>New Bern, North Carolina
>
--
Steve Mills
@Bath Potters Supplies
Dorset Close
Bath
BA2 3RF
UK
Tel:(44) (0)1225 337046
Fax:(44) (0)1225 462712
Eleanora Eden on sat 23 aug 97
I've looked through all the responses on this and don't see any mention of
paperclay though there's lots of talk about clay body. Seems like it would
be a good situation for adding paper pulp.
Eleanora
At 12:00 AM 8/20/97 EDT, you wrote:
>----------------------------Original message----------------------------
>I have made hundreds of 1/4" to 3/8: thick tiles measuring 5 x 6 to 8 x 12
>but now I'm trying to make one piece table tops, they measure 1" to 1 1/2"
>thick and are 14 " hexagons and EVERY time they crack right across the
>middle, if not in the bisque then in the glaze. Anyone have any ideas?
>Thank you in advance
>Janet Francoeur
>New Bern, North Carolina
>
>
Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101 eden@sover.net
| |
|
