ferment, and injures them by making them hard and brittle. We see, then,
the importance of "scouring" wool for the removal of "yolk," as it is
called, dirt, oil, etc. If this important operation were omitted, or
incompletely carried out, each fibre would be more or less covered or
varnished with greasy matter, resisting the absorption and fixing of
mordant and dye. As scouring agents, ammonia, carbonate of ammonia,
carbonate of soda completely free from caustic, and potash or soda
soaps, especially palm-oil soaps, which need not be made with bleached
palm oil, but which must be quite free from free alkali, may be used. In
making these palm-oil soaps it is better to err on the side of a little
excess of free oil or fat, but if more than 1 per cent. of free fat be
present, lathering qualities are then interfered with. Oleic acid soaps
are excellent, but are rather expensive for wool; they are generally
used for silks. Either as a skin soap or a soap for scouring wools, I
should prefer one containing about 1/2 per cent. of free fatty matter,
of course perfectly equally distributed, and not due to irregular
saponification. On the average the soap solution for scouring wool may
contain about 6-1/2 oz. of soap to the gallon of water. In order to
increase the cleansing powers of the soap solution, some ammonia may be
added to it. However, if soap is used for wool-scouring, one thing must
be borne in mind, namely, that the water used must not be hard, for if
insoluble lime and magnesia soaps are formed and precipitated on the
fibre, the scouring will have removed one evil, but replaced it by
another. The principal scouring material used is one of the various
forms of commercial carbonate of soda, either alone or in conjunction
with soap. Whatever be the form or name under which the carbonate of
soda is sold, it must be free from hydrate of soda, _i.e._ caustic soda,
or, as it is also termed, "causticity." By using this carbonate of soda
you may dispense with soap, and so be able, even with a hard or
calcareous water, to do your wool-scouring without anything like the ill