PULPING BROKE

107

1. Soaking in Tanks.—This method is used mostly in mills making low-
grade papers, such as middles or wrappers, where the presence of uncleared
bits is of little consequence. The paper, mostly waste paper of low quality,
is put into tanks with water, the charge being pressed down with poles in
order to save space. After soaking for one or two days the pulp is dug out
and filled into the beaters.

2. Boiling in Rotary Boilers.—The two essentials are combined by this pro-
cess, but the disintegration is not complete unless after prolonged treatment.
Paper that has been boiled is reduced in 'quality'; if the boilers revolve at
a sufficiently high speed—3 revolutions per minute—excellent disintegration is
obtained. If too much water is used, size is boiled out and is lost, and the strength
of the fibres is very much lessened.

For this reason, many paper-makers prefer to defibre the broke by means

[Messrs. Massm, Scott and Co. Ltd.
FiG.33.—THE 'PERFECT* PUIPER: SECTION SHOWING THE REVOLVING SHAFT AND FIXED ARMS
of a kollergang or kneader after a light boil in either a stationary or rotary
boiler.
3. Breaking in Potchers followed by Steeping in Draining Tanks.—An old
hollander beater is generally used. The broke is filled in with water and heated
by blowing in steam to nearly boiling point. After the potcher has been fully
charged the broke is roughly broken for a short time and then run into
draining tanks. When the water is drained away, the pulp is dug out for
the beaters. This is a very expensive way of treating broke, owing to the
power required to break the paper and the steam used to heat the consents
of the potcher.
4. Breaking in Special Pulping Engines with Steam or Hot Water, without
Preliminary Treatment.--rfkh is die best and cheapest method and is now being