Placing
pieces in the kiln, especially in oval and side fired kilns, is not
about filling the kiln completely. Kilns have hot and cold spots,
and the arrangement of the elements can have an effect too.
The
first thing to determine with a new kiln - and immediately after any
alterations to the kiln - is where the hot and cool areas of the kiln
are. There is an extensive guide to this on the Bullseye site. In
short, the method is to place strips of glass on short kiln furniture
all around the kiln at the level(s) you will be firing. These strips
should be of equal size and the kiln furniture the same distance
apart. Take the temperature slowly up to slumping temperature.
Observe when the visible glass pieces begin to slump. Let that
continue until they are about half way down. Then proceed to the
anneal. When cool you can open the kiln and see the areas where the
glass has slumped most – the hotter areas – and where it has
slumped least – the cooler areas. This will give you information
on areas to avoid if you want an even finish all around the edges.
If
your kiln is side fired, you need to consider the shelf placement in
relation to the elements. The best arrangement is to have one
element below the shelf and the shelf between elements so the radiant
heat is not directly onto the edge of the shelf as that may lead to
breaks.
Put
glass on the shelf as centrally as possible. If the glass must be
near the elements, baffle the glass from the direct radiant heat from
the side elements.
