The steel used was 1/8 inch galvanised after forming
and welding, there is no reason why heavy stainless could not be used.
Plain steel would have a very short life.
The internal tube fitting into the pot must be a tight
fit and securely fixed to the pot or stack as the design allows a sweeps
brush to enter inside it for cleaning. A modification for very dirty fuel
would be to have the external tube made so it could be detachable from
the internal to allow cleaning of the gap between tubes.
One made to this design impedes the sparks of a size
likely to cause damage, I have seen one that was on top of a chimney fire
that burned off the galvanising and bent the metal, no other damage was
found other than the whole stack had cracked in the heat.
Use only dry, well seasoned wood, good quality coal
or peat, avoid overfilling the fire – a little fuel often is best.
Give careful consideration to the state of the stack
and ideally have it lined.