at the yarn at is about 150 deg. F.;
too high a temperature must be avoided, as with increased heat the
tendency to felt is materially augmented, and felting must be avoided.
The hanks are treated for about twenty minutes in the liquor, and are
then wrung out, drained, and again treated in new scouring liquor for
the same length of time. After rinsing in cold water they are dried
and finished.

When the oiled wool has been spun into yarns, whether worsted or (p. 028)
woollen, and passes into the hands of the dyer, it is necessary to
remove from it all the oil before any dyeing operations can be
satisfactorily carried out. This oil is removed by the use of soap and
weak alkaline liquors, using these at about 110 deg. to 120 deg. F. The
most common way is to have the liquor in a rectangular wooden tank, and
hang the hank of yarn in by sticks resting on the edges of the tank;
from time to time the hanks are turned over until all the oil has been
washed out, then they are wrung out and passed into a tank of clean
water to wash out the soap, after which the yarn is ready for dyeing.

When the yarn is of such a character that it is liable to curl up,
shrink and become entangled, it is necessary that it be stretched
while it is being treated with the soap liquor; this is effected by a
stretching apparatus consisting of two sets of rollers connected
together by a screw attachment, so that the distance between the two
sets of rollers can be varied. The hanks are hung between each pair of
rollers, and can be stretched tightly as may be required.

For pressing out the surplus liquor from the hanks of yarn a pair of
squeezing rollers is used.

#Scouring Woollen Piece Goods.#--Very often before weaving the yarns are
not scoured to remove the oil they contain, as the weaving is more
conveniently done with oily yarn than with a scoured yarn. Before
dyeing the oil must be taken out of the pieces, and this can be
conveniently done by scouring in a washing machine such as is shown in
figures 7 and 8, using soap and soda liquors as before, and following
up with a good rinse with water.

[Illustration: Fig. 7.--Cloth-washing Machine.]

The soap liquors used in scouring yarns and pieces become charged with
oil, and they should be kept, and the oil recovered from them together
with the fatty matter of the soap, by treatment with sulphuric acid.
By subjecting the grease or fatty matter so obtained to a boil with
caustic soda soap is