o the
corrugated rolls, or the first break, where it is partially flattened
and slightly crushed and a small amount of flour, known as the break
flour, is separated by means of sieves, while the main portion is
conveyed through elevators to the second break, where the kernels are
more completely flattened and the granular flour particles are partially
separated from the bran. The material passes over several pairs of rolls
or breaks, each succeeding pair being set a little nearer together. This
is called the gradual reduction process, because the wheat is not made
into flour in one operation. More complete removal of the bran and other
impurities from the middlings is effected by means of sieves,
aspirators, and other devices, and the purified middlings are then
passed on to smooth rolls, where the granulation is completed. The flour
finally passes through silk bolting cloths, containing upwards of 12,000
meshes per square inch. The dust and fine debris particles are removed
at various points in the process. The granulation of the middlings is
done after the impurities are removed, the object being first to
separate as perfectly as possible the middlings from the branny portions
of the kernel. If the wheat were first ground into a fine meal, it would
be impossible to secure complete separation of the flour from the
offal portions of the kernel.

[Illustration: FIG. 39.--EXTERIOR OF FLOUR MILL AND WHEAT ELEVATOR.]

Flour milling is entirely a mechanical process; the flour stock passes
from roll to roll by means of elevators. According to the number of
reductions which the middlings and stock undergo, the milling is
designated as a long or a short reduction system; the term 4, 6, 8, or
10 break process means that the stock has been subjected to that number
of reductions. With an 8-break system of milling, the process is more
gradual than with a 4-break, and greater opportunity is afforded for
complete removal of the bran. In some large flour mills, the wheat is
separated into forty or more different products, or streams, as they are
called, so as to secure a better granulation and more complete removal
of the offals, after which many of these streams are brought together to
form the finished flour. What is known as patent flour is derived from
the reduction of the middlings, while the break flours are recovered
before the offals are completely removed; hence they are not of so high
a grade. No absolute definition can be