RUNNING THE MACHINE 227

settling on the wire, and when it bursts, it is usually too far advanced towards
the suction box for the hole to be closed up again. The remedy is to use as
much water with the stuff as is possible, to fill the space again that has been
made by the bursting of the bubble. Beating the stuff finer, or running at a
slower speed, will also effect an improvement. Entrained air and other gases,
sometimes caused by the chlor-lignins, also cause these froth spots.

Froth is often a great nuisance on the machine, and sprays should be pro-
vided to keep it down as much as possible.

A little extra alum will sometimes be of great assistance, or a little paraffin

[Oven, S<* ml Wa*
FK. 92.—WOTE Row.
run into the stuff from a tin above the chutes by means of a woollen thread,
whore this is otherwise permissible. ,
Sfe&ti Heating of SfcdL—Iflhe efiect of raising the temperature of the stuff
and water on the foarttiire is to make it work more 'free'. Advantage is
taken of this fact when making heavy substances OT running highly fibrillated
stock. By raising the temperature to about 90° to 95° F. an extraordinary
change in the working of the stuff oa tbe wire can be observed. The fibres
swell up and become more rigid, the meshes of the wire open a little owing
to the expansion of the metal* and, chiefly important, the tenuity of the water
is increased and its surface tension lessened. The effect of these things is that
the work of the suction boxes, and consequently the strain on the wire* is
made much less. More water and shake can then be used and a closer and more