pan is gently removed,
and the soap may be either ladled out and conveyed to the frames, or
withdrawn by the aid of a pump from above the nigre through a skimmer
(Fig. 1), and pipe, attached by means of a swivel joint (Fig. 2) (which
allows the skimmer pipe to be raised or lowered at will by means of a
winch, Fig. 3), to a pipe fitted in the side of the pan as fully shown
in Fig. 4, or the removal may be performed by gravitation through some
mechanical device from the side of the copper.

[Illustration: FIG. 1.--Skimmer, with flange for attachment to
skimmer-pipe.]

Every precaution is taken to avoid the presence of nigre in the soap
being cleansed.

[Illustration: FIG. 2.--Swivel-joint.]

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 neces