You still remember the sentences from the starting page?
(A kiln is simply a structure where heat is applied inside.  The source of this heat can be …)

The simplest kiln is a barrel where the greenware (unfired ceramics) and the fuel will be mixed putted inside.

The heat of the fire will be more homogeneous and a bit more efficient (compared to a open bonfire) but it’s far away from a controlled fire. Means cracks, caused by heat stress, will still appear.