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Loading a Kiln
Orton Firing Tip -
LOADING A KILN FOR BEST RESULTS
Reprinted with the permission of the Edward Orton Jr. Foundation
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Loading
a kiln for firing is not a simple matter of placing shelves and
stacking ware. The more thought and planning that is put into loading,
the better the results. Ware and shelf placement, the size of the load,
the firing characteristics of the kiln and the type of ware being
firing are all important factors.
First the Furniture
Kiln shelves come in all shapes and sizes. For economy of space, it is
best to choose shelves similar in shape and size to your kiln chamber.
For instance, use a round or multi-sided shelf in a round or
multi-sided kiln. Keep the size small enough so there is at least 1" of
space between the shelf edge and the side of the kiln or the
Kiln-Sitter. Also allow some room between the top of your ware and the
lid of the kiln and leave space for witness cones amongst your ware.
Select posts in heights to accommodate the ware you are firing. Leave
some room between the kiln shelves for air to flow, for heat transfer
and for removal of fumes.
Half shelves are very useful to improve air movement in the kiln. Use
two side by side with a 1/2" space between them and you don't lose much
stacking space.
Some kiln manufacturers recommend placing shelves directly on the floor
of the kiln. Most suggest using 1" posts to put the bottom up from the
cooler floor. This creates an insulating layer much like a storm door.
Setters and Stilts
Air movement in the kiln is clearly a big consideration - one of the
most important when loading a kiln. Ceramics need to heat uniformly to
prevent warping and stresses in the ware. Air needs to move around
shelves and around individual pieces.
Plates and tiles benefit from the use of tile and plate setters or
stackers. Shelf style setters allow air to move under the large flat
objects so they heat more evenly. Avoid heating large flat objects
directly on the cooler shelf. If you are firing decorated tiles or
plates, vertical setters economize on space, and sets can be stacked to
fit even more.
Glazed ware needs to be stilted or dry footed or the melting glaze will
stick the ware to the kiln shelf, ruining both. Stilts also provide
space for air to move around all sides of the ware. Porcelain and
stoneware can not be stilted. The stilts embed into the ware during
firing. Instead, use high fire kiln wash or silica sand on the shelf.
Use prop to prevent sagging of porcelain.
Consider Heat Distribution
It is important to evaluate heat flow in your kiln and to make this a
consideration in loading. Use pyrometric cones to determine the heating
characteristics of your kiln so you know where the hot and cooler
places are. Arrange your ware with different sized pieces on the same
shelf to allow better heat flow.
Don't Overfill
Perhaps one of the most important factors in good fired results is
enough air to mature the ware - to burn out organics in bisque and
develop best colors in glazes. Shelf and ware placement and the use of
setters and stilts can all help this, but here are a couple more tips:
1. When stacking bisque, invert bowls and mugs opening to opening
instead of nesting- this helps air move around all sides of a piece and
prevents black rings and spots in the bottom of ware.
2. Fire bisque lids and bottoms together. To get the best fit for lids,
fire them on the piece they match. This will let the two pieces shrink
together so you get a good tight fit. Fire all glaze pieces separately.
3. Leave space between ware - don't overfill. There is a temptation to
cram as much as possible into the kiln to economize on firing costs.
Ware fired too closely together creates firing problems. If you must
overfill, fire very slowly and vent adequately.
4. Mix thin and thick-walled pieces together throughout the load don't
concentrate them in one area where they are competing for air and heat.
5. Use downdraft venting to move air through the kiln and to remove fumes created during firing.
Want to learn more?
Read more about Firing Reds in the Orton Firing Line and Technical Tips
publications. Each issue is packed full of articles to help you learn
more about firing. Members of the Orton Firing Institute receive these
publications at no charge. Single copies are available to non-members
at a per issue rate. Orton's 80 minute video, Key Principles of
Successful Firing, is also an excellent resource on firing.
For information on Orton products, see your Orton dealer or
distributor. For information on the Firing Institute or publications,
contact:
Orton Firing Institute
PO Box 460
Westerville, OH 43086
(614) 895-2663 |
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