Aluminum is used to make alloys of various kinds, the most important of which is aluminum bronze. This alloy is made up of from 5 to 8% aluminum and from 92 to 95% copper. It is used to imitate gold, is very rigid and strong, and is not affected by air or water. Hence it is valuable for many purposes. Just before it is poured from the cupola, steel from which castings are to be made has added to it small quantities of aluminum and bronze. This insures that the castings will be free from blow-holes. Lately, a new flash-light powder containing aluminum has been placed on the market.