John,
In steps 3 and 10 "Dry stone in sun for 3 or 4 days or in an oven."
What temperature do you use? It should be low so as not to subject the stone to thermal shock.
Gary
Well, to be pedantic, it’s not the temperature you reach that causes ‘thermal shock’, but how quickly the temperature changes.
It would be quite possible to heat a piece of sandstone up to around 800°C, providing you spent about 2 days heating up and another 2 days cooling down, but heat it up to 200°C and drop it in a bucket of water and it will likely split.
--
Barry
