54

MODERN PAPER-MAKING

'brown'. Hot-ground pulp is that which is torn off the log in the presence
of very little water, so that the contact point is made hot by the friction of the
stone and the pressure employed. This hot-ground pulp is said to work less
free than the ordinary cold-ground, but more difference is often observed
between two consignments of cold-ground than between hot- and cold-ground
pulp.

Cold-ground pulp is ground with a sufficiency of water to keep the stone

[Boving and Co.

FIG. 14.—BATTERY OF KAMTR GRINDERS

cool and carry off the fibres. The third quality-is made from logs that have
been steamed or boiled before grinding, and is a stronger-fibred pulp. About
25 per cent more power is required to grind the cooked logs.
The pulp fibres, after being carriecl away from the grinders, are put through
strainers and over a presse-pate machine or concentrator.
Any coarse particles which will not pass through the screen or strainer may
be collected and re-grouad.