From the stone depends on the method used for heating the stone shape, size and type. Metal stove heats the casing stones planes, so the stones must be placed no more than two layers on the heated surface. The stones should be large – a fist- sized (10-15 cm). They are good warm up from the metal accumulate enough heat to steam.
Stones are heated in electric ovens electric heating elements arranged in the stone tank short distances from one another. This ensures a uniform heating of the stones. There used smaller stones – from 5 to 7 cm.