Can I use a pizza stone or a tile for the shelf?
Yes. but, you need to be consider how flat the stones are.
Choose the flattest, smoothest stones you can find. Take a ruler or other straight edge with you
to select the flattest. Hold the
straight edge vertically, and look for light coming from between the edge and
the surface of the stone. Choose the
ones with the least light showing.
You can make the stones very flat and smooth when you get
them to your studio. Put the surfaces
together face to face and move one against the other in a circular motion. After minute or so of grinding, lift and take
note of the areas which are showing the effects of the grinding. Where the
stone has not been affected, are the low spots.
The number and depth of the low spots will determine whether you wish to
continue to even out the variations in the surfaces.
You can speed the grinding by putting a slurry of grit
between the two surfaces. You can use a
coarse grit of 100 or less in the grinding. Place a small pile of the grit and
make a depression in which to put the water.
Mix into a runny paste. And place
the other stone on top and begin to move the upper stone in multiple directions.
Keeping the grinding surfaces damp will prevent any dust
from the grinding getting into the air. You will hear a difference in sound
when the slurry begins to dry out. This
is the time to add a spritz of water to the grinding materials. As you check from time to time, you will see
the areas that already are ground and those that are not yet evened. The grit will remain in the depressions and
be clear from the higher areas. Push the
grit onto those clear areas to continue the smoothing and flattening process. Continue until the surfaces of both stones
are smooth and flat. This probably will
not take much more than a quarter of an hour.
It is advisable when smoothing ceramic or glass materials to
wear a dust mask. The dust from both are irritants, although not
carcinogenetic.
When the stones are smooth, they need to be carefully dried. If you have the time, you can leave them to
air dry for a few days. Even then you
need to fire them to just below the boiling point of water and soak there for
several hours. Keep the vents open, or
the door/lid propped open slightly.
It will continue to be important to fire up slowly to keep
the stone from breaking from thermal shock.
The most rapid expansion of the ceramic is in the 200⁰C to 250⁰C range.
This means that the rate of advance of firings should be slow until 250⁰C has
been passed, no matter what the glass might survive.
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