Service manual

2 Hold the straight edge firmly and score the glass
with the glass cutter. Press just hard enough so that
the scoring noise sounds steady and unbroken.
3 Place the straight edge under the glass so that an
edge is lined up with the score line you just made.
Press down on the glass. It will break cleanly.
Fusing Compatibility
of Glass
When glass changes temperature, it expands and con
-
tracts. The rate at which glass changes size is called the coef
-
ficient of thermal expansion. If you fuse two glass pieces to
-
gether and one changes size faster or slower than the other,
the fused piece may crack—even several months after fus
-
ing.
When different glasses have a close enough coefficient of
expansion to fuse successfully, they’re called fusing compati
-
ble. Buy glass labeled fusing compatible. Or fuse glass that
has been cut from the same sheet, which guarantees com
-
patibility.
Fusing Compatibility Test
1 To test glass for compatibility, fuse small ½” square
sample pieces of different glasses onto a larger base
piece of clear transparent. The base should extend
beyond the small sample pieces by half an inch on
each side. Include, among the sample squares, a
piece cut from the clear transparent base.
2 Heat the glass to a temperature that completely
rounds the edges of the small sample pieces.
3 After the glass cools, place a polarizing filter under
the glass and another filter over the glass. Look at
the glass with light shining through it (hold it over a
lamp). Turn one of the filters until the filters are at
their darkest.
Results of the Test
If you see a halo around the edges of the small glass sam
-
ples, the glass is not compatible. If you see no halo, the glass
is fusing compatible.
Why did we include a sample square cut from the base
transparent glass? It tests for annealing. A halo around that
piece means the glass was not annealed properly. Perform
the test again, this time cooling more slowly through the an
-
nealing range.
The Annealing Range
Each type of glass has a temperature range that it must
pass through slowly when it cools. This is called the anneal
-
ing range. This slow cooling gives hot glass time to release
the stress of cooling. If you cool the glass too fast through the
annealing range, it will break.
The larger and thicker the glass, the slower it must pass
through its annealing range. You cannot over-anneal, so err
on the side of caution if you aren’t sure how long to anneal.
Small projects such as earrings rarely need annealing time as
they cool.
Cleaning and Gluing
the Glass
Grease, dirt, and finger
-
prints etch permanently
into the glass during firing.
Clean the glass with glass
cleaner (the type without
silicones), rubbing alcohol,
or even plain water just be
-
fore assembling the pieces
on the kiln shelf.
Use white glue, such as
Elmer’s diluted 1:1 with wa
-
ter, to hold the glass pieces
together after you place
them on the kiln shelf. Use
the glue sparingly. Glue is
especially important when
fusing wire into the glass.
The glue prevents the glass
or wire from moving out of
place before they fuse. The glue disappears during firing.
Avoid using glue on the coated side of dichroic glass. If
you lay dichroic glass carefully onto the piece, glue is unnec-
essary, so avoid it altogether if you do not know which side of
the dichroic is coated.
Load Glass Into the Kiln
Air should circu
-
late between the shelf
and the bottom of the
kiln, so place three or
four 1/2” posts in the
kiln. Lay the shelf
over the posts.
Firing the Glass
Firing speed varies depending on the size and thickness
of the glass project. The thicker and larger the project, the
slower you must fire it. Otherwise the glass may crack. Small
jewelry pieces, such as earrings, can usually fire at full speed.
Viewing the Glass During Firing
Watch the glass by moving the top over just enough to
where you can see inside the kiln. Look for several seconds at
a time. Wear firng safety glasses and protective gloves.
Note: When you move the top, do not slide it, or dust
particles could land on the glass. Gently lift it
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