92 MODERN PAPER-MAKING
which is the cause of the trouble at the machine when making thick papers
from highly fibrillated stock.
The finished sheet has its strength from the 'fibrillated' condition of its
mass, which is the essential factor, and not from the water which has clung to
the fibrillse, and, being only incidental to the condition, has been removed.
This explanation of what happens in the beater is supported by paper-
making practice and common sense, and it seems to us that in no way, except
by the exercise of power, can we achieve this particular condition of stock.
Attempts have been made to reduce the time and power required for the
fibrillation of the stock by producing a formation of mucilage or sHme by means
of acids or alkalis.
No success seems to have attended these experiments, which were, indeed,
doomed to failure, because they were based on a false hypothesis—namely,
that wet, greasy or slimy stock must be productive of a strong paper.
A moment's thought would have shown that the reduction of a fibrous
material to a starchy paste could not increase its strength. The condition
aimed at in these experiments does, however, come nearer to that to which the
true meaning of the word 'hydrated' may be applied. But it is of interest
to note that the wetness obtained gave no additional strength or quality to
the paper, or, at the most, only what would have been achieved in greater
degree by mixing a quantity of good starch with the fibres in the beater.
There are, however, well-known methods of improving the strength and
hardness of paper by adding adhesive substances to the pulp in the beater.
These substances simply glue the fibres together at the presses and drying
cylinders of the machine. None of these in general use at present, however,
will give the increase in strength which may be obtained by skilful fibrillation.
We think that, instead of trying to fit mysterious explanations to what is,
after all, a very simple mechanical process, chemists should turn their attention
to the discovery and application of some substance, or chemical compound,
which, when mixed with ordinary cheap paper-making material, will give a
paper with strength and qualities equal to those of a weU-fibrillated sheet made
from cotton and linen fibres.
Hbrilktion, with its great consumption of power, would then give place
to die cheaper method we call 'free3 beating, and our object would be attained.
RJEHNING
After stock has been beaten in the hollander or other beater of the same
type, andl>efore it can be let down to the machine chests, it is necessary to set the
roll so as to 'dear' the fibres. This clearing consists in breaking or brushing out