The ebullition from the formation of carbonic oxide puffs up the resultant phosphoric slag enough to make most of it run out of the furnace, thus both removing the phosphorus permanently from danger of being later deoxidized and returned to the steel, and partly freeing the bath of metal from the heat-insulating blanket of slag.
It actually puffs up the wood to the level of the surface, or at least close if the scratch is not too deep.
Cover the bowl with plastic and allow to rise for about one hour, until the dough puffs up.
The pancake puffs up while baking and then falls once it is removed from the oven.
