Not all steep slumps are deep.
|An example of a deep, steep slump|
|An example of a soup bowl with steep sides|
|A square bowl with slightly less steep sides|
|A shallow plate or platter|
Relative to the size, the above platter mould is a steep slump, although not deep.
This can be slumped in two stages to obtain confirmation of the glass to the mould without distortion.
One way to do this is to place powdered kiln wash in the mould so there is a gentle curve to the bottom. Place glass on the mould and do a slow, low temperature slump.
After first slump, empty the kiln wash back into your container (it can still be used as kiln wash). Fire again using the same slow low temperature schedule as for the first.
It may also help to retain the rim on the shallow plate to cut your circle 12mm larger than the diameter of the mould. This will allow a margin for the slight shrinking that even a low and slow temperature slump will cause.