The Chemistry of Hat Manufacturing | Page 5

externally coated with a firmly adhering layer of flat
overlying scales, with not very even upper edges, as you see. The upper
or free edges of these scales are all directed towards the end of the hair,
and away from the root. But when you look at a hair in its natural state
you cannot see these scales, so flat do they lie on the hair-shaft. What
you see are only irregular transverse lines across it. Now I come to a
matter of great importance, as will later on appear in connection with
means for promoting felting properties. If a hair such as described, with
the scales lying flat on the shaft, be treated with certain substances or
reagents which act upon and dissolve, or decompose or disintegrate its
parts, then the free edges of these scales rise up, they "set their backs
up," so to say. They, in fact, stand off like the scales of a fir-cone, and
at length act like the fir-cone in ripening, at last becoming entirely
loose. As regards wool and fur, these scales are of the utmost
importance, for very marked differences exist even in the wool of a
single sheep, or the fur of a single hare. It is the duty of the wool-sorter
to distinguish and separate the various qualities in each fleece, and of
the furrier to do the same in the case of each fur. In short, upon the
nature and arrangement and conformation of the scales on the
hair-shafts, especially as regards those free upper edges, depends the
distinction of the value of many classes of wool and fur. These scales
vary both as to nature and arrangement in the case of the hairs of
different animals, so that by the aid of the microscope we have often a
means of determining from what kind of animal the hair has been
derived. It is on the nature of this outside scaly covering of the shaft,
and in the manner of attachment of these scaly plates, that the true
distinction between wool and hair rests. The principal epidermal
characteristic of a true wool is the capacity of its fibres to felt or mat
together. This arises from the greater looseness of the scaly covering of
the hair, so that when opposing hairs come into contact, the scales
interlock (see Fig. 9), and thus the fibres are held together. Just as with
hair, the scales of which have their free edges pointing upwards away
from the root, and towards the extremity of the hair, so with wool.
When the wool is on the back of the sheep, the scales of the woolly hair
all point in the same direction, so that while maintained in that attitude
the individual hairs slide over one another, and do not tend to felt or

mat; if they did, woe betide the animal. The fact of the peculiar serrated,
scaly structure of hair and wool is easily proved by working a hair
between the fingers. If, for instance, a human hair be placed between
finger and thumb, and gently rubbed by the alternate motion of finger
and thumb together, it will then invariably move in the direction of the
root, quite independently of the will of the person performing the test.
A glance at the form of the typical wool fibres shown (see Fig. 10), will
show the considerable difference between a wool and a hair fibre. You
will observe that the scales of the wool fibre are rather pointed than
rounded at their free edges, and that at intervals we have a kind of
composite and jagged-edged funnels, fitting into each other, and thus
making up the covering of the cylindrical portion of the fibre. The
sharpened, jagged edges enable these scales more easily to get under
the opposing scales, and to penetrate inwards and downwards
according to the pressure exerted. The free edges of the scales of wool
are much longer and deeper than in the case of hair. In hair the
overlapping scales are attached to the under layer up to the edges of
those scales, and at this extremity can only be detached by the use of
certain reagents. But this is not so with wool, for here the ends of the
scales are, for nearly two-thirds of their length, free, and are, moreover,
partially turned outwards. One of the fibres shown in Fig. 10 is that of
the merino sheep, and is one of the most valuable and beautiful wools
grown. There you have the type of a fibre best suited for textile
purposes, and the more closely different hairs approach this, the more
suitable and valuable they become for those purposes, and vice versâ.
With regard to the curly structure of wool, which increases the matting
tendency, though the true cause