STOVING OR DRYING POWDER.
Drying.
A drying-room, heated by steam pipes, is fitted with open framework shelves, on which rests small wooden trays about 3ft. long, 1ft. 6-in. in breadth, and 21⁄2in. deep, having canvas bottoms; on each is spread 8lbs. of powder. This room holds about 40 barrels, or 4,000lbs., which remains in it for twenty four hours, and is subjected to a heat of 130° Fahrenheit for sixteen hours, communicated by steam passing through pipes arranged horizontally on the floor of the room. The temperature is raised and lowered gradually, otherwise the too sudden change would be likely to destroy the texture of the grain. The ceiling and roof are fitted with ventilators, through which all the moisture escapes, so that there is a constant current of hot air circulating through the room. It is of the greatest importance that the vapour should be carried off; for, if this is not effectually done, on the decrease of temperature, it would return to its liquid state, and form again on the powder.