Service manual

After the kiln begins firing, leave the top closed. Do not
lift the top until it is time to remove the clay. Visual inspec
-
tion of the clay during firing is unnecessary.
If you are firing glass with the silver clay, on the other
hand, you will need
to check the fusing
progress of the glass
by moving the kiln
top ½” or more and
looking inside.
Look for just a sec
-
ond or two. As you
gain experience, you
will be able to pro
-
gram the correct
temperature for the silver clay and glass combination, elimi
-
nating the need to visually check the glass.
Manual Kilns: Select the type of silver clay that has the
shortest hold time. You will need to adjust the switch during
hold to correct the temperature as it drifts.
Cooling Time
After the clay silver has fired to completion, you can lift
the top an inch to speed cooling. If you are firing stones,
glass, or other materials with the silver clay, it will be safer to
allow the kiln to cool slowly with top down. Remove the piece
when the kiln reaches room temperature.
Combining Silver Clay
With Other Materials
There are two ways to fire silver clay with other materials
such as glass:
I
Fire the silver clay first by itself. After you have cleaned
and polished the silver clay, fire it a second time with
glass.
I
Fire the silver clay and other materials, such as a stone,
together in a single firing.
Glass is often fired with the silver clay in a single firing.
Many types of glass, however, will melt at silver clay tempera
-
tures. If you are going to combine glass and silver clay in a
single firing, test a small sample of the glass. To do this, fire
the glass during a silver clay firing, keeping the glass sepa
-
rate from the silver clay piece. (This way you won’t ruin the
silver clay piece.)
Place the pieces on a ceramic fireclay shelf. You must coat
the shelf with glass separator, or otherwise the glass sample
with embed into the shelf.
If the glass sample survives the firing, you can fire that
type of glass with silver clay in a single firing. Note, however,
that different types of glass fire to different temperatures.
Every time you fire a different type of glass, be sure to test.
Firing Mistakes
Silver Clay
Cracks that appear in fired silver clay may be due to too much
water in the silver clay before it was fired. Another cause is
careless handling of a dried piece before firing. To repair, fill
the crack with silver clay and fire again.
Brittle Silver clay will not reach full strength if underfired.
You may be able to save the piece by firing again to the correct
temperature and hold.
Too Much Shrinkage When silver clay is overfired, it
shrinks too much and loses detail. You may need to replace the
thermocouple on the digital kiln if the temperature is
inaccurate.
Glass
Glass Cracking is caused by heating or cooling too fast or
fusing incompatible glass. Not enough glass separator on the
shelf can also cause glass cracking.
Most problems in fusing are caused by rushing the firing.
The glass must change temperature slowly during the criti-
cal temperature range of 100° - 500° F. This critical range
applies to both heating and cooling.
The second critical temperature range is annealing,
which is the cooling range of 950° - 750°F average. Cool the
glass slowly during this range so the stress in the glass will
have time to dissipate.
If you become impatient after the glass has fused and you
tilt the kiln for a few seconds to peek inside, you may hear a
“ping,” which is the sound of glass cracking. Avoid the temp-
tation to open the kiln. Wait until the kiln has cooled to room
temperature. Some artists schedule their fusing so that it is
completed before they go to bed. That way they will be asleep
while the glass cools and they won’t be tempted to open the
kiln while it is still hot.
After each firing, examine the shelf. Recoat if the kiln
wash is chipped. When glass sticks to a bare section of shelf,
the glass will crack.
Glass Bubbles are often caused by heating the kiln too fast.
Air, grease or dirt trapped between layers of glass can cause
bubbles. Other causes are uneven glass volume, and moisture
or air trapped between the glass and shelf.
Make sure the shelf is completely dry before firing. If you
have applied fresh glass separator, leave the shelf in the kiln
at 300°F for 30 minutes before placing glass on it.
One way to eliminate bubbles is to hold the temperature
at 100°F below fusing temperature for 20 minutes. This
gives the shelf time to heat up to match the temperature of
the glass.
Glass Separator Sticks To Glass when fired too hot. In
-
stead of firing to a full fuse temperature, try firing 50°F cooler
and holding at that temperature for twenty minutes.
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