Using stone in the presence of fire

["daedelus lanthanien" <daedeluslanthanien@zzzzzzzzzzz>]

Hello Jerry, nice to meet you.

Never, Never do this again. It is very dangerous. Always try to use
firebrick, fired clay, pumice, or a clinker mix to do this. The other fellas
seem to like soapstone but I have never used it. One can get away with a
large airgap if you would like, but keep the fire within limits. I would not
let the fire get within 2 feet of the stone at any time, especially when the
infrared is hitting it squarely.(This does NOT mean you may use stone 2 feet
over the fire! This is a HORIZONTAL rule! NOT verticle!)  Keep in mind that
robust fires can cause heat to sink through even firebrick. The stone will
swell from the heat and introduce thermal stresses that will wreck even the
finest of laid stonework. Let a good airgap behind them and do not touch
them with the stone, of course with the exception of closing the collars at
the front of the firebox door. Sometimes I will fill in the firebrick collar
with a good unpacked insulation for increased thermal resistance. Also keep
in mind that firebrick need to be kept dry in a exterior environment.
Fashion doors and a flue cap for the project to protect it when it is not
being used. Wet firebrick can explode too. Over time, if let wet, water will
leach out the acids in the brick, thus lowering their thermal qualities.