102 MODERN PAPER-MAKING
There is, however, another reason which accounts in no small measure
for the easy fibrillation; it is, in fact, that the linen cloth, in the case of new
cuttings or used rags, has had much more hard usage during its existence prior
to its arrival at the mill.
The linen fibre, being itself hard and harsh, produces a correspondingly
hard thread and cloth. This cloth is so harsh and lacking in suppleness that
it is unsuitable for clothing or household use until it has been softened and
made pliable by the linen cloth manufacturer. To effect this softening the
cloth is beaten, or 'beetled', as it is called, by wooden beetles, or clubs, so
that someone else has a hand in the fibrillation of the stuff before it is put to
its various domestic uses. Again, linen being hard wearing, it lasts many years
in the form of sheets, tablecloths, etc., and in consequence it is laundered many
times more than a similar article of cotton.
All these things help in the preparation of the rags for the beater, so that
by the time the Hnen stock has been broken into half stuff in the beater, it is
already well fibrillated and feels wet and greasy to the touch.
The amount of linen which can be used in the furnish is really limited by
the length of the machine wire and the efficiency of the suction boxes; for if,
with 25 per cent of linen, the paper can just be couched without crushing, it
is no use to bring up die proportion of linen to 35 or 40 per cent. This will
only give the machinemen endless trouble trying to get the water out, and the
appearance of the sheet will be spoilt without any appreciable gain in the ultimate
strength of the paper.
In general, if linen is to be used, it will be found advantageous not to use
too much, but to get full value from a moderate amount by carefully beating
it with blunt tackle, and so defibring it that it will entwine and bind together
the rest of the furnish and give that characteristic hardness to the finished sheet.
When the furnish is to be 25 per cent of linen and 75 per cent of other
fibres, beaten separately in four engines, it will generally be found best to
furnish the linen first and leave the other fibres till last, as it will be the last to
reach a satisfactory state of fibrillation, providing that the tackle in all beaters
is in the same state.
Never beat a naked furnish of cotton and linen in the same beater if it can
possibly be avoided, for, unless the amount of linen is small, the amount of
roll required to beat it will destroy the cotton, and the result mil be worse
than if no linen had been used.
Wood Pulp.—So far we have been dealing with materials that require heavy
beating or cutting. That is to say, a great deal of power is consumed by the
beating engine, in the one case for fibrillating and in the other for cutting
fibres.