The temperature at which soap may be cleansed depends on the particular grade--soaps requiring to be liquored should not be cleansed too hot or a separation will take place, 150 deg. F. (66 deg. C.) may be taken as a suitable temperature for this class of soap; in the case of firm soaps, such as milling base, where cooling is liable to take place in the pan (and thus affect the yield), the temperature may be 165 deg.-170 deg. F. (74 deg.-77 deg. C.). This latter class of soap is generally run direct to the frames and crutched by hand, or, to save manual labour, it may be run into a power-driven crutching pan (neutralising material being added if necessary) and stirred a few times before framing. [Illustration: FIG. 3.--Winch.] [Illustration: FIG. 4.--Soap-boiling pan, showing skimmer pipe, swivel and winch.] [Illustration: FIG. 5.--Hand crutch.] [Illustration: FIG. 6.--Mechanical crutcher.] _Crutching._--This consists of stirring the hot soap in the frames by hand crutches (Fig. 5) until the temperature is sufficiently lowered and the soap begins to assume a "ropiness". Crutching may also be performed mechanically. There are various types of mechanical crutchers, stationary and travelling. They may be cylindrical pans, jacketed or otherwise, in the centre of which is rotated an agitator, consisting of a vertical or horizontal shaft carrying several blades (Fig. 6) or the agitator may take the form of an Archimedean screw working in a cylinder (Fig. 7). [Illustration: FIG. 7.--Mechanical crutcher.] The kind of soap to be crutched, whether thin or stiff, will determine the most suitable type for the purpose. The former class includes "washer" soap which is generally neutralised, and coloured and perfumed, if necessary, in these crutching pans, and in that case they are merely used for mixing the liquids with the hot soap prior to its passage along wooden spouts (Fig. 8) provided with outlets over the frames, in which the crutching is continued by hand. In the case of stiff soaps requiring complete incorporation of liquor, the screw type is preferable, the soap being forced upwards by the screw, and descending between the cylinder and the sides of the pan, while the reverse action can also be brought into play. The completion of crutching is indicated by the smoothness and stiffness of the soap when moved with a trowel, and a portion taken out at this point and cooled should present a rounded appearance. When well mixed the resultant product is emptied directly into wheel-frames placed underneath the outlet of the pan. It is important that the blades or worm of the agitating gear be covered with soap to avoid the occlusion of air and to prevent the soap becoming soft and spongy. [Illustration: FIG. 8.--Wooden soap spout.]