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making flat tiles and keeping them flat

updated thu 19 jan 06


Ravenstone Tiles on wed 18 jan 06

I saw the postings on the clayart list from April and others about
warping tiles. We've read a lot about sandwiching tiles between
drywall (sheetrock), flipping them, turning them, covering them, etc.
I can tell you that none of this is necessary. Why spend countless
hours handling, coddling and fussing over tiles? Not efficient! Not
cost effective for a professional tile-maker. I have developed a
technique that is almost 100% foolproof for making flat tiles and
greatly minimizes the amount of handling needed. I hope it may be
useful to some of you out there.

First, you need to use a heavily grogged clay that is sculptural or
tile quality, not a throwing clay (not plastic). I use an off-white
stoneware called Crystal Stone that fires to cone 6. (I usually glaze
fire to cone 5 - 6 after a bisque firing of cone 05.) Crystal Stone
is available at Seattle Pottery Supply. I probably tested dozens of
clay bodies before I found this one, with the least warping and least
shrinkage of all their clays that I tried. I'm sure other pottery
suppliers will offer something that's similar.

Second, I like the clay on the dry, stiff side. Too much water makes
it dry slowly and promotes warping. Wedge it a lot if it is too wet.

Third, supplies you will need: several pieces of drywall (small
enough to handle easily, like 18" by 24" in size, also tape the edges
with duct tape to avoid that nasty plaster interior from leaving dust
everywhere); rolling pin or slab roller; trimming knife; a pattern
slightly larger than the final size of tile you want (my clay shrinks
about 10% so I make my pattern large enough to compensate for that);
a couple sturdy metal racks, the type you find for closet organizers.
Available at Target, K-Mart, or hardware stores. The racks are used
for drying. An oven rack might also work. The bars need to be fairly
close together to support your tiles fully. (Tip: thrift stores, junk
stores, & salvage stores often have these racks for sale at a
fraction of the retail cost.)

To begin, I cut approx. 1" thick slabs off my bag of clay. Wedge the
clay as needed. Then I hand roll the slab with a sturdy rolling pin
in both directions to get the approximate thickness needed. Most of
my tiles are press-molded in plaster molds. If you use molds, drop
your completed tile right onto a piece of drywall as it releases from
the mold.

If you don't use molds, don't worry. The tile making process works
the same way without molds. Just roll out your slabs directly onto a
piece of sheetrock using wooden spacers or dowels beneath your
rolling pin for the correct thickness. (I like 1/2" thick tiles
myself). Once you have rolled the clay slabs out, don't move them!
Don't lift them or turn them or anything. (If you do move the clay,
it will remember and will warp, bend and curl during drying and
firing.) Just trim the slabs in place, cutting them to the desired
dimensions using your trimming knife and pattern. Remove the scrap
clay around the edges and rewedge. Allow the tiles to sit on the
sheetrock for 8 to 12 hours give or take a couple hours (overnight is
usually good). That drywall will suck a lot of water out of the clay!

Now your tiles will be stiff enough to handle without flexing; test a
tile and see if you can pick it up safely. At this point trim and
smooth the tiles' edges and then place them directly onto a rigid
metal storage rack. Because air circulates on all sides of the tiles,
they dry very evenly and no warping occurs! No flipping is needed. No
covering is needed. No weighting or stacking is needed. Keep the
tiles on the rack until they are completely dry and ready to bisque
fire. There is no need to score the backs of tiles unless you want
to. This has nothing to do with the warping or drying process. It
helps the tile adhesive cling to the tile and hold it to the wall or
floor during installation.

In all, you should only need to handle your green tiles about three
times: once to roll out and cut the clay; once to smooth the tile
edges and place it on a drying rack, and once to put it in a kiln for
your bisque firing. I fire tiles flat on the kiln shelf both for
bisque and glaze firing. I have made tiles by the thousands, big and
small, and perhaps have a warped tile once in every hundred.

Other notes: While your tiles dry, avoid direct sources of warm air
(like a register vent or portable heater) that might dry one area
faster than another. You want nice even drying, at top and bottom.
At 55 to 60 degrees in my studio, my tiles take about a week to fully
dry with no warping. If you want to hurry the drying you may use a
fan to gently circulate the air in the room; this might dry the tiles
in a few days. Drying will be slower in a cool damp environment.

I built my tile drying rack from two shelf units made of rigid metal
rod. Each shelf unit measures 12" wide by 36" long. My two racks are
supported side by side on a wooden framework with legs that holds
them in the air. The total drying surface from these two racks is 24"
wide by 36" long. It will hold quite a few tiles. Its good to have
the racks well off the ground and allow plenty of air to circulate.
Because I make lots of tiles, I bought enough racks to have several
levels available to dry tiles, all supported by the wooden framework.
(You could support the racks between two chairs or counters or
improvise something if you don't want to build a permanent drying rack.)

I hope this is helpful.

Laura Reutter
Ravenstone Tiles
1633 Cherry St.
Port Townsend, WA 98368