nsidered as a crystallisation of the soap, in which the impurity forms
the colour.

_Blue and Grey Mottled Soaps._--These are silicated or liquored soaps in
which the natural mottling, due to the impure materials used in the
early days of soap-making, is imitated by artificial mottling, and are,
consequently, entirely different to curd mottled soaps.

The materials employed in making mottled soap comprise bleached palm
oil, tallow, bone fat, cocoa-nut oil, palm-kernel oil, cotton-seed oil,
and, in some instances, rosin.

The choice of a charge will naturally depend upon the cost; the property
of absorbing a large amount of liquor, which is characteristic of soaps
made from cocoa-nut oil and palm-kernel oil, is taken advantage of, as
are also the physical properties of the various fats and oils, with a
view to the crystallisation of the resultant soap and the development of
the mottle. The fat is saponified, grained and boiled on strength, as
previously described. After withdrawing the half-spent lye, the soap is
just closed by boiling with water, and is then ready for the silicate or
other saline additions.

Soap intended to be liquored with silicate of soda should be distinctly
strong in free alkali; the crystalline nature of the soap is increased
thereby, and the mottled effect intensified. Some makers, however, fit
the soap coarsely and allow a nigre to deposit; then, after removing the
nigre, or transferring the settled soap to another copper, containing
scraps of mottled soap, get the soap into a condition for mottling, and
add the silicate of soda solution. To every 1 cwt. of soap, 28 lb. of
silicate of soda solution, 32-1/2 deg. Tw. (20 deg. B.) is added, whilst
boiling; the strength of the silicate solution, however, will depend
upon the proportion of cocoa-nut oil and palm-kernel oil present in the
charge. Many soap-makers use 20 deg. Tw. (13 deg. B.) (cold) silicate solution,
whilst others prefer 140 deg. Tw. (59.5 deg. B.), with the gradual addition of
water to the soap, kept boiling, until the product is in the correct
mottling condition, and others, again, use bleach liquor, soda crystals,
pearl ash, and salt, together with silicate solution.

Considerable skill and experience is necessary to discern when the soap
acquires the correct mottling state. It should drop off the spatula in
large thick flakes, take considerable time to set, and the surface
should not be glossy.

When this mottling condition