CHAPTER XIV
PAPER-MAKING ON THE MACHINE-WATER-MARKING
Notes on Machine—General.—As paper-making on the machine varies so
very much with the qualities, substances, etc., of paper, it would he futile to
attempt to lay down hard-and-fast rules as to how the various parts of the
machine should be used. The machineman has to exercise his judgment, and
must have at his command numberless 'dodges', if we may be allowed to
call them so, for getting the results he wants.
As far as the strainers there is little that may be called 'paper-making'.
It is when we get the stuff to the wire that the art and skill of paper-making
commence. The slices are the first consideration, and these have more to do
with the look and strength of the sheet than may he supposed. On some
machines there is a lifting gear to raise or lower the breast roll end of the wire
frame. A low level will cause a deep 'dam' to form behind the slices, and a
deep pond will remain after them. Under the influence of the shake this might
be expected to close up the texture of the sheet, but it is not always so. The
rising slope of the wire will result in the stuff and water rolling over and turning
on itself, and a cloudy, though well water-marked, paper will be made. This
is what is generally wanted for laid ledger papers of a certain class.
By raising the breast end a Me the stuff will flow out from the slices more
freely, and though not being so long under the influence of the shake, will
produce a closer-looking sheet.
The same result can be obtained by increasing the speed of the machine,
and taking the stuff away from the slices before it can get time to roll back.
Thus if the breast end is fixed at one level, the speed of the machine may be
used to do the same work as a lifting gear. Again, if we have a deep dam
behind the slices—i.e., the slices close down on die wire—the stuff will shoot
oat and forward, and go well up the wire, and get very little good from the
stake. Also, the fibres will be turned round and set on edge by being forced
ikoegb a very fine ojpening. This makes a raw and badly water-marked sheet.
By raising tbe slices the fibres will flow gently on to the wire, and the shake
vn& get hold of them at once where the longest throw occurs. Then the fibres
wifl be wefl felted and closed up, and the sheet will be found to be stronger
and door in texture and have a dearer water-mark.
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