Baked molds, of course, are comparatively rigid. As the risers which stand on top of the flanges and other high parts of castings aid in resisting the natural shortening of long castings during and after “setting” of the metal, there is great liability that the still red-hot casting will crack somewhere along its length. It is therefore necessary to loosen with bars the sand of the mold as soon as the metal of the casting has set, particularly between the risers, and to break out the sand of the core inside, around which the shrinking metal might crack were the sand left in its hard packed condition. After the casting is shaken out from the mold, it is cleaned and the risers cut off either by sawing or with the more modern oxy-acetylene torch flame. [Illustration: OTHER TYPICAL STEEL CASTINGS ] Steel castings should be annealed in order to “refine,” i.e., make finer the grain of metal and to equalize “strains” which are set up in the castings during cooling. Coarse grain and internal strains tend to make the castings brittle. No such extended annealing, however, is necessary as is the case with malleable cast iron, for no divorcing of carbon from the iron with separation of free carbon is possible. The castings are carefully heated to a temperature of about 1600° or 1700° Fahrenheit and allowed to cool slowly. After annealing, they are cleaned and excrescences removed by chipping, after which the castings are tapped, drilled or otherwise machined according to the purposes for which they are intended. [Illustration: CAST STEEL VALVES, STEAM SEPARATOR, AND DIRECT-RETURN TRAP FOR USE WITH SUPERHEATED STEAM ] While more costly in manufacture and installation than are those of cast iron, valves, fittings and other cast steel products are, so far as we now know, practically permanent. Their notable shock resisting quality is well shown in the following table which is reprinted from page 188. [Illustration: POURING STEEL INTO MOLDS FROM A BOTTOM-POUR LADLE ] It is to be noted that while malleable cast iron far surpasses “semi-steel” in this property, though their tensile strengths are ordinarily somewhere near the same, cast steel, in turn, offers more than six times the resistance of the malleable iron to shock and has nearly double its tensile strength. It is this great strength and resistance to shock, heat and pressure, with freedom from “permanent growth” under alternate heatings and coolings that make cast steel such a valuable material for the many purposes for which castings are to-day employed. Millions of steel castings annually find varied application.