For "beating," the stock is thrown into a large revolving tub. Rag and
wood fibre may be mixed in different proportions, according to the
grade of the paper wanted. The stock is then washed a little to be
sure that it is clean and white. Water at first is mixed in with the
fibre until it is so diluted that it will flow freely; then it is
beaten for several hours by means of an iron wheel covered with iron
or steel knives about one-quarter of an inch thick, which revolves
over an iron bed-plate with similar knives. During this beating
process, clay is mixed with the stock, mainly to give the paper a
well-filled and better appearance, and not, as most people think, to
add weight, although this is sometimes an object. Sizing material is
also added, which helps to keep the fibres together and hold the ink
in printing. If it is desired to give the paper a white shade, a small
amount of aniline blue or pink is mixed in; otherwise it is called
"natural" or "unblued."

The beating part of the process of paper making is the most important.
The stock has to be beaten up so that all the fibres are separated and
broken into just the right lengths according to the weight and
strength of the paper to be made. The harder the roll is set down on
the bed plate, the shorter the fibre will be and _vice versa_, but if
the roll is not put down hard, the stock has to be beaten so much
longer.

"Machining" may be divided into five processes:--

_First._ When the stock leaves the beater it is run into a large
"stuff" chest, and is continually being stirred so that it will not be
lumpy. By this time the pulp is about as clean as possible and is
ready for the paper machines. The first thing to be done on the
machine is to dilute the stock with pure water to the consistency of
buttermilk, according to the thickness of the paper required. Then
this liquid stock runs through what are called "sand settlers," which
are supposed to collect what dirt, iron, etc., remain.

_Second._ From the sand settlers the stock runs on to a screen,
through which it is drawn by means of suction. This process prevents
fibres which are lumpy and too long from getting on to the machine,
and allows only those of a certain size and length to go forward to be
made into paper. An endless and very fine wire cloth, which is
continually moving at the same rate of speed as the rest of the paper
machine, takes the stock after it has been screened. This is the first
step tow