|How to Avoid Warped or Cracked
Handmade Ceramic Tile
HOW TO DRY FLAT CLAY
WITHOUT WARPING IT
Hint #1: Potter's Wheel
Hint #2: Firing
Stacks of Greenware Plates
Hint #3: Setting
the cone packs in the kiln.
Hint #4: Preventing
Stuck Lids with Lid Wax
Hint #5: Preventing
Warped & Cracked Tile
Hint #6: Preventing
Cracked Slab Boxes
Tile factories use huge presses to form tile from clay that has only
6 percent moisture. It stays flat because there is essentially no
WHY DO TILE WARP AND CRACK
Those of us who make tile from moist clay know that it shrinks a lot
when it dries. If tile is on the shelf to dry, this uneven shrinkage
will warp tile into something like potato chips, or if you weight it down,
it will often crack. You cannot "force" it to stay flat.
THE GENERAL PRINCIPLE
Dry it in a way that allows the water to leave at the same rate from
both sides at once. On larger tile, faster edge drying causes cracks
across the center in many cases.
Here are several ways to accomplish uniform
two sided drying (flat shrinkage). None of these methods is 100 percent
fool proof, but with practice they work.
Flip them frequently during the day and cover with them plastic during
the night. If they have started to warp, you can sometimes pat them flat
with a paddle after they are too dry to bend.
Dry them on wire racks (like old refrigerator shelving) that have LOTS
of air space under them. Four inches of air space under each layer
is minimum. I have mounted some wire closet shelving in our ceramics
room where it is high enough to be "out of the the way".
Sandwich them between dry sheets of gypsum board (drywall)(sheetrock).
This is paper covered plaster and it draws moisture from both surfaces.
Scrap drywall is available free from housing construction sites.
Cut one side with a utility knife and bend it to make pieces to fit your
storage places. If you tape the edges with packaging tape or duct tape,
you avoid the problem of plaster pieces getting into the clay rework. Be
sure it is unpainted so it absorbs moisture. These moist boards can
be trashed or after complete drying they can be reused for another project.
PROTECTING THE EDGES WHILE DRYING
None of the above
solutions deal with the faster drying of edges. I use one or more
of the following methods to minimize this problem. Small pieces may
not need any special edge protection while drying.
List of Hints for PottersHint
#1: Potter's Wheel
For more hints, come back soon. Your
comments are welcome.
Coat the edges with wax resist. This is water soluble liquid wax
used for decoration. It becomes waterproof as it dries.
Leave scraps of clay slab butted tightly against all the outside edges.
Place plastic sheeting tightly against the edges or plastic strips wrapped
on the edges.
Double the clay thickness at the edges. This can be done temporarily
by laying strips of clay on the edges and removing them after drying is
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