be incorporated with them than materials producing soaps of
less body. Rosin imparts softness to a soap, and also colour.

This is a fitted soap and full details of manufacture have already been
given.

Cheaper soaps are produced from lower grade materials hardened with
alkaline solutions.

_Resting of Pans and Settling of Soap._--The fitted soap is allowed to
settle from four to six days. The period allowed for resting is
influenced, however, not only by the size of the boil, and the season,
but also by the composition of the soap, for if the base has been made
from firm stock it is liable to cool quicker than a soap produced from
soft-bodied materials.

On subsidence, the contents of the pan will have divided into the
following:--

First. On top, a thin crust of soap, with perhaps a little light
coloured fob, which is returned to the pan after the removal of the good
soap.

Second. The good settled soap, testing 62-63 per cent. fatty acids. The
subject of removing and treatment of this layer is fully dealt with in
the next chapter.

Third. A layer of darker weak soap, termed "nigre," which on an average
tests 33 per cent. fatty acids, and, according to the particular fit
employed, will amount to from 15-20 per cent. of the total quantity of
soap in the pan.

The quantity of nigre may vary not only with the amount of water added
during finishing, but is also influenced by the amount of caustic alkali
remaining in the soap paste prior to fitting. If the free caustic
alkali-content is high, the soap will require a large amount of water to
attain the desired fit. This water renders the caustic into a lye
sufficiently weak to dissolve a quantity of soap, consequently, as the
"nigre" is a weak solution of soap together with any excess of alkali
(caustic or carbonate) and salt which gravitates during the settling,
the quantity is increased.

Fourth. A solution containing alkaline salts, mostly carbonates and
chlorides, with a little caustic.

The amount of the layer is very variable, and doubtless, under certain
physical conditions, this liquor has separated from the nigre.

_Utilisation of Nigres._--The nigres are boiled and the liquor separated
by graining with salt. Nigre may be utilised in various ways.

(1) It may be used several times with new materials. This particularly
refers to soaps of the "Washer" type. The colour of the nigre will
determine the number of times it can be employed.

(2) It may be