ly by means of
water.

[Illustration: FIG. 18.--Automatic stamper.]

In the case of household soaps, where the resultant product must be of
good appearance and have a firm texture, the difficulty is to produce a
bar fit for sale after the cooling has been performed, as soap which has
been suddenly chilled lacks the appearance of that treated in the
ordinary way. Several patents have been granted for various methods of
moulding into bars in tubes, where the hot soap is cooled by being
either surrounded by running water in a machine of similar construction
to a candle machine, or rotated through a cooling medium; and numerous
claims have been made both for mechanical appliances and for methods of
removing or discharging the bars after cooling. In many instances these
have proved unsatisfactory, owing to fracture of the crystalline
structure. Moreover, in passing through some of the devices for
solidification after chilling, the soap is churned by means of a worm or
screw, and this interferes with the firmness of the finished bar, for,
as is well known, soap which has been handled too much, does not regain
its former firmness, and its appearance is rendered unsatisfactory.

A form of apparatus which is now giving satisfactory results is the
Leimdoerfer continuous cooler (Fig. 19). This consists of a fixed
charging hopper, A, a portable tank, B, containing tubes, and a
detachable box, C, which can be raised or lowered by means of a screw,
D. The bottom of the hopper is fitted with holes corresponding with the
cooling tubes, _e_, and closed by plugs _c_, attached to a frame _b_,
which terminates above in a screw spindle _a_, by means of which the
frame and plugs can be raised and lowered so as to permit or stop the
outflow of soap into the cooling tubes. The tubes are closed at the
bottom by slides _d_, and the box B, in which they are mounted, is
carried on a truck running on rails. The charging hopper can be
connected with the soap-pan by a pipe, and when the hopper is filled
with liquid soap the plugs _c_ are raised and the air in the box C
exhausted, thus causing the soap to descend into the cooling tubes.

[Illustration: FIG. 19.--Leimdoerfer cooler.]

The slides _d_ are closed, the screw D released, and the box B moved
away to make room for another. At the end of the rail track is an
ejecting device which pushes the cooled soap out of the tubes, and the
truck is run back on a side track to the machine for use over