The soft fancy toilet soaps are divisible into two classes: 1. good
_potash soap_, coloured and scented in various ways, forms the basis of
the Naples and other ordinary soft soaps of the perfumer; 2. _pearl
soap_ (_savon nacré_), which differs from the other both in physical
aspect and in mode of preparation.
_Ordinary soft Toilet Soap._--Its manufacture being conducted on the
principles already laid down, presents no difficulty to a man of
ordinary skill and experience; the only point to be strictly attended
to, is the degree of evaporation, so as to obtain soap always of uniform
consistence. The fat generally preferred is good hog’s lard; of which 30
pounds are to be mixed with 45 pounds of a caustic lye marking 17° on
Baumé’s scale; the temperature is to be gradually raised to ebullition,
but the boil must not be kept up too long or too briskly, till after the
_empatage_ or saponification is completed, and the whole of the lye
intimately combined with the fatty particles; after this, the
evaporation of the water may be pushed pretty quickly, by a steady boil,
till copious vapours cease to rise. This criterion is observed when the
paste has become too stiff to be stirred freely. The soap should have a
dazzling snowy whiteness, provided the lard has been well refined, by
being previously triturated in a mortar, melted by a steam heat, and
then strained. The lard soap so prepared, is semi-solid, and preserves
always the same appearance. If the paste is not sufficiently boiled,
however, it will show the circumstance very soon; for in a few days the
soap will become gluey and stringy, like a tenacious mass of birdlime.
This defect may not only be easily avoided, but easily remedied, by
subjecting the paste to an adequate evaporation. Such soaps are in great
request for shaving, and are most convenient in use, especially for
travellers. Hence their sale has become very considerable.
_Pearl soft Soap._--It is only a few years since the process for making
this elegant soap became known in France. It differs little from the
preceding, and owes its beautiful aspect merely to minute manipulations,
about to be described. Weigh out 20 pounds of purified hog’s lard on the
one hand; and 10 pounds of potash lye at 36° B. on the other. Put the
lard into a porcelain capsule, gently heated upon a sand-bath, stirring
it constantly with a wooden spatula; and when it is half melted, and has
a milky appearance, pour into it only one-half of the lye, still
stirring, and keeping up the same temperature, with as little variation
as possible. While the saponification advances gradually, we shall
perceive, after an hour, some fat floating on the surface, like a film
of oil, and at the same time the soapy granulations falling to the
bottom. We must then add the second portion of the lye; whereon the
granulations immediately disappear and the paste is formed. After
conducting this operation during four hours, the paste becomes so stiff
and compact, that it cannot be stirred; and must then be lightly beaten.
At this time the capsule must be transferred from the sand-bath into a
basin of warm water, and allowed to cool very slowly.
The soap, though completely made, has yet no pearly appearance. This
physical property is developed only by pounding it strongly in a marble
mortar; whereby all its particles, which seemed previously separated,
combine to form a homogeneous paste. The perfume given to it, is always
essence of bitter almonds; on which account the soap is called _almond
cream_, _crème d’amandes_.