This tutorial came from GlassCampus.com and is full of excellent information. Check out their website for many more informative tutorials!
Using Casting Molds
PREPARING THE MOLD
Carefully clean the mold to remove any dust and
scrub out any remaining kiln wash from previous
firings. Single-use kilnwash like “Hotline” is
preferable to multiple-use kilnwash like “Bullseye”
because it’s easier to scrub out. An old used
toothbrush is an effective tool for removing kilnwash
or a bristle brush on a Dremel will speed up the job.
Prepare the mold with 3 or more coats of thin kiln
wash. More thin applications are better then few
thick coatings. Be careful to not apply so much kiln
wash that you fill in all the detail in the mold. Don’t
just coat the inside part of the mold that will be filled
with glass, but also coat the top upper surface. Any
small pieces of glass that are left on that surface
will become permanently embedded into the mold if
you don’t.
FILLING THE MOLD
The glass level will drop as it melts into the mold.
Take care to be sure you have enough to fully fill
the mold. The smaller the pieces of glass you use,
the less it will sink. On average, the finished
casting will be about half the depth of the loose
filled mold. Because the glass level drops, you may
prefer to fill part of the mold with a pieces of glass
stood vertically to provide the extra glass needed to
fully fill your mold.
FRIT & POWDER
Glass powder and very fine frit doesn’t stay
transparent but will turn slightly opaque making the
finished casting looking more like alabaster then
glass. Some attractive special effects can be
achieved by putting small amount of glass powder
in the details of the casting and filling with larger
pieces of a different colour.
FIRING SCHEDULE FOR CASTING (COE 96)
1. 800 dph to 1475°F hold 20 min
2. FAP to 960°F hold 30 min
3. 600 dph to 300°F OFF
FINISHING THE CASTING
Your casting will have some spikes along the
edges. You can cold finish to remove them – either
by hand or with a grinder or wet belt sander. The
casting will also have some texture from the mold.
You can remove the texture and smooth off the
scratches from cold finishing by turning the casting
over and returning it to the kiln to fire polish.
FIRING SCHEDULE for FIRE POLISH
1 500 dph to 1000°F hold 20 min
2 1500 dph to 1300°F hold 5 min
3 FAP to 960°F hold 60 min
4 500 dph to 200°F OFF min
The above firing schedules are for COE 96 glass.
For COE 90 add 20°F to all top temperatures.
For float glass add 50°F.
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