The furnace treatment just described burns out almost all of the usual impurities in iron, but this treatment produces a slag or cinder of iron oxide and silica which mixes with the iron and forms a sheath around each iron crystal.

Fig. 19.

When the puddler has formed a ball for removal from the furnace, his helper takes it out by means of a pair of heavy tongs suspended from an overhead trolley, and pushes it over to the squeezer.

This machine (Fig. 19) consists of a heavy cast-iron casing B, within which revolves a rough-surfaced cast-iron cylinder 0. The space A between the cylinder and the casing is wide at one opening and somewhat narrower at the other. The cylinder is constantly revolving slowly, and when the puddle ball starts at D, it is rolled and squeezed until it emerges at E. This operation presses out masses of cinder with more or less violence and noise. Fig. 20 shows a squeezer for heavy work.

Fig. 20. - Squeezer for 400-lb. Bloom.

Fig. 21. - Puddle Rolls.

The bloom emerging at E, Fig. 19, still at a high heat, is immediately grasped with heavy tongs and started through the rolls shown in Fig. 21. The end of the bloom is presented first to the largest pass, b, and when it has gone through this pass, it is sent back over the top of the upper roll and is in turn run through the entire seven passes. Some cinder is pressed out, and the iron particles are pressed into a more tenacious mass. The last pass, which is near the center of the rolls, leaves the bar about 6 inches wide and less than an inch thick.

This product is known as much bar or puddled bar. The rolls have elongated the iron crystals, giving the bar a fibrous structure, and each fiber is enclosed in a thin sheath of cinder, with streaks of cinder between many of the fibers.