CHAPTER VI
BEATING
beaters - beating- rehning
the beater may perform several operations besides its chief function of actually
fibrillating the stuff.
First, it may have to break up sheets of wood pulp or lumps of rag stuff.
This is done by feeding in or furnishing the sheets or lumps of stuff gradually
after the beater is about half or three-quarters full of water.
The sheets of wood pulp should be wetted first, or pushed under water
before they reach the roll, in order that they may be as soft as possible. Li
the same way the lumps of rag half stuff, which are usually damp, should be
torn up small by hand as they are being thrown in.
During this period of .furnishing the roll is raised up well away from the
plate, to prevent it jumping up when any hard lump of stuff comes between
it and the plate.
In a surprisingly short time the sheets of wood or lumps of rag are reduced
to a fairly uniform pulpy mass. In the case of the rag stuff, the first treatment
depends to a great extent on how far the rags and threads have already been
reduced in the breaker. Usually, however, a great many twisted cotton threads
are still present, and these have to be drawn out by the roll.
As soon as this is accomplished the beating proper begins, and the roll
must be let down to a fairly hard rub. Just how much pressure can safely be
brought to bear on the stock-depends on the strength of it when it is furnished,
and mis must be left to the skill and experience of the beaterman. When the
beating has been carried far enough, and it is found on examination that the
fibres on the whole are too long, the roll must be let down heavily on to
the plate for a short time to cut some of the longer fibres to a length suitable
for the paper which is to be made.
Finally, the stuff must be cleared—that is, the little clumps and knots of
fibres must all be separated out-otherwise hard lumps may get through, and
may either clog up the strainers or, if they are small enough, find their way
into the finished sheet.
The treatment of wood pulp is much the same as rags, except that there
are no threads to be drawn out; nothing but small clumps of fibres have to
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