Cress E18, Руководство пользователя, Страница: 19 / 28

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It is important always to stand pyrometric cones at the pre-cut angle provided by the base of each cone; this
should be approximately 8 degrees away from vertical in the direction the cone is expected to bend. Setting the
cones consistently at this angle assures that each cone (of the same number) will bend at uniformly the same
temperature. Cone plaques or wire cone holders are commercially available. Holders may also be made from
brick or clay. Holders made from fire brick are generally reusable and trouble free. Standard cones may also
be purchased with wider self-supporting bases.
Periodically view the witness cones during firings. The kiln should shut off at about the time the cones
bend to a 90 degree angle. This cone will continue to bend a little after the kiln is shut off as the cooling is
slow. This effect is more dominant at lower cone numbers.
Placing at least one cone (more if you wish to check temperature uniformity) in each firing, even if
not visible from a peephole, is a good idea since noting its condition when you unload the kiln will confirm
that the load was properly fired.
An excellent way to check the temperature on any shelf in any location in the kiln is to use a cone
plaque containing three large cones. One is for the desired maximum firing temperature. The other two should
be numbered above and below the firing cone. For example, if firing to cone 06, use a cone 05, 06, and 07.
These are often referred to as the guide cone, firing cone, and guard cone. The lower temperature (guide) cone
bends as a warning that the desired temperature will soon be reached. The firing cone should bend until the tip
is at a 90 degree angle, and the guard cone, if bent too far, signals overfiring.
Be sure to keep pyrometric cones bone dry so that they will not crack in the kiln. Once dropped, roughly
handled or exposed to moisture, cones develop small cracks which tend to make them bend prematurely and
give an inaccurate temperature indication.
The cones generally used in firing clays and glazes in pottery work are numbered ranging from 07 to
04. A very common one which works satisfactorily in most cases is 06. Cones used to fire china paint, gold,
and decals range from 015 to 019. Cone 4 to cone 6 is used for porcelain. Stoneware may be fired to cone 8 or
cone 10. All clay and glaze manufacturer’s recommend the correct heat treatment for their products. Clays and
glazes do vary, so check labels or ask your local ceramic supply dealer for advice on the proper cones to use,
since he knows the characteristics of the clays and glazes he handles.
FIRING
A kiln is designed to produce the extremely high temperatures necessary to chemically alter ceramic
materials. Use caution and common sense to avoid burns when the kiln is in operation, since the kiln surfaces
will be hot. It is therefore imperative that you read and observe all safety precautions.
Safety cautions
Do not leave the kiln unattended, such as firing over night. Even though your kiln has an electronic
control, it is advisable to use a large cone visible through the peephole to check firing progress. Check witness
cones at (1) hour intervals through firing, at the expected shutoff time and every half hour thereafter until the
cone is properly bent or the control has turned off. Always check to see that the control has operated correctly.
Always monitor the progress of each firing.
Never open the lid while the kiln is firing. This could cause serious burns as well as damage to the
ware and kiln. After firing always allow the kiln to cool with the lid closed until it is cool enough for you to
unload it with your bare hands.
A two position lid prop is provided. The highest lid prop position is used for normal venting at the
beginning of the firing cycle. It operated simply by rotating a prop to engage the catch mounted on the lid.
After the kiln reaches 1000 degrees F, release the prop by raising the lid by the handle (use protective glove)
so that the prop swings out of the way, and gently lower the lid. The lowest lid prop position is used for the
later portion of the firing cycle for china, lusters, and gold firing to obtain the best results.
The peepholes, as the name implies, allow you to look into the kiln and, along with witness cones
placed on the shelves, to monitor firing progress. In most instances, the kiln is fired with the lower peephole
plugs in place and the top most peephole open.