After the soap has been thoroughly milled it is ready for plodding. A _plodder_ is so constructed as to take the soap ribbons fed into the hopper by means of a worm screw and continuously force it under great pressure through a jacketed cylinder through which cold water circulates in the rear to compensate the heat produced by friction and hot water at the front, to soften and polish the soap which passes out in solid form in bars of any shape and size depending upon the form of the _shaping plate_ through which it is emitted. The bars run upon a _roller board_, are cut into the required length by a special _cake cutting table_, allowed to dry slightly and pressed either automatically or by a foot power _press_ in any suitable soap _die_. The finished cake is then ready for wrapping and after due time in stock reaches the consumer. Besides the various apparatus mentioned above there are many other parts for the full equipment of a modern soap plant, such as remelters, pumps, mixers, special tanks, power equipment, etc. As has been stated, however, practical experience will aid in judging the practicability as to installation of these. The various methods of powdering soap are, however, not generally known. Where a coarse powder is to be produced, such as is used for common washing powders, no great difficulty is experienced with the well known Blanchard mill. In grinding soap to an impalpable powder the difficulties increase. The methods adapted in pulverizing soaps are by means of disintegrators, pebble mills and chaser mills. The disintegrator grinds by the principle of attrition, that is, the material is reduced by the particles being caused to beat against each other at great velocity; a pebble mill crushes the substance by rubbing it between hard pebbles in a slowly revolving cylinder; the chaser mill first grinds the material and then floats it as a very fine powder above a curb of fixed height. The last method is particularly adapted for the finest of powder (140 mesh and over). CHAPTER III Classification of Soap-Making Methods. In the saponification of fats and oils to form soap through the agency of caustic alkalis, as has been stated, the sodium or potassium salts of the mixed fatty acids are formed. Sodium soaps are usually termed hard soaps, and potassium soaps soft. There are, however, a great many varieties of soaps the appearance and properties of which depend upon their method of manufacture and the oils or fats used therein. The various methods adopted in soap making may be thus classified: