a. 
a 
436 
PULP AND PAPER MAKING. 
During the nineteenth century there were remarkable changes and im- 
provements in the methods employed for converting paper stock into 
paper pulp and paper. These advances have been due to two causes—one, 
the revolution in the nature and supply of the raw material itself, and 
the other, the increased demand for the finished product. The method 
of preparation of paper pulp or half-stuff has thus far largely been de- 
pendent upon the nature of the material treated, whereas the making of 
the pulp into finished paper in sufficient quantities to meet the marvelous 
growth of the industry has caused the laborious hand process to be super- 
seded by the huge automatic machines of the present time. However, 
the principles involved in the making of paper remain unaltered, regard- 
less of whether the material is removed from a vat with a small hand 
sieve and turned out a single sheet at a time or is allowed to flow on to 
an endless wire cloth web under heavy rolls and over the steam-heated 
drying cylinders of a Fourdrinier machine. Generally speaking, the 
purpose is just the opposite of that which obtains in the isolation of 
fibers for the textile and cordage industries; instead of so treating the 
fibrous substance as to preserve the fiber bundles or filaments in their 
greatest length, it is necessary, by some mechanical or chemical means, 
to convert them into the individual fibers or cells of which the filaments 
are composed. 
There are five distinct steps in the preparation of paper pulp from any 
vegetable material. Two of these are entirely mechanical, whereas the 
remainder are of a distinctly chemical nature. Arranged in their order 
of procedure, they are: 
1. Cleaning —A purely mechanical process which consists in removing 
all foreign matter such as sand, dirt, weeds, chaff, ete., either by hand 
or machinery. 
2. Boiling or digesting.—This results in eliminating the soluble plant 
constituents and incrusting matter by chemical means. 
3. Bleaching consists in further chemically purifying the resistant cel- 
lulose by removing adhering coloring matter. 
4. Beating or refining—This procedure mechanically disintegrates 
the pulpy mass of fibers into fragments of requisite length. 
5. Loading, sizing, and coloring so modify the bleached and beaten 
pulp by the addition of mineral or animal substances, that a nonporous, 
resistant surface of the required shade is given to the finished product. 
BOILING OR DIGESTING. 
At the present time there are two main groups of processes in general 
use for the isolation of paper cellulose, namely, the alkaline and acid 
treatments. The first and older method depends upon the action of 
solutions of caustic soda, soda ash, caustic lime, or mixtures of these 
