anywhere from 1 hour to 10 to 12 hours, depending upon the character of the rags and the strength of the bleaching agent. The rags are given a thorough washing to remove the remaining traces of the bleaching agent, and the rag mass is then drained.

OTHER PULPS

STRAW

Straw pulp is made largely from the straw of wheat or rye, although oat straw, too, is frequently used. Straw pulp is made chiefly into paper or board for use as a corrugating material in shipping containers. For such use, straw pulp lends to the board a stiffness and a resiliency which are highly desirable.

Straw pulp, combined with waste-paper pulp, is used in the manufacture of mailing tubes and set-up boxes.

The cooking of straw for corrugated paperboard is done in large spherical rotary digesters, which hold from 6 to 7 tons of the raw product. Milk of lime is the cooking liquor most commonly used. For the softer types of board the cooking time averages from 10 to 12 hours; upon completion of cooking, the whole is dumped to drain and season. The pulp mass is then beaten and washed, the washing process being continued until all traces of the cooking liquor have been removed.

JUTE

Jute fiber comes from between the bark and the wood of the jute plant, an annual which grows in India. The fiber is of unusual strength and is produced for use in twine and burlap. Only old jute, such as sacking, burlap, and string, is used by the paper maker, as the cost of the original material is too high to permit its use in the production of paper.

Jute is made into pulp in much the same way that rags are handled. Washing and bleaching follow the general rag procedure of dusting and cooking. The jute pulp produces a paper of excellent strength and durability, particularly adapted to the manufacture of tough wrapping paper, covers, and tags. Jute pulp is much used in mixture with kraft pulp.

HEMP

Of the hemp fibers, manila hemp is by far the most important one used in paper making. Hemp pulp, too, is frequently used in mixture with kraft pulp. Because of the great strength of the manila hemp fiber, pulp made of manila rope makes particularly strong bags which are frequently used for heavy substances such as cement and plaster. Such pulp is also used as the insulation layer surrounding the individual wires making up telephone cables.

Manila fiber for pulp is obtained through the collection of old rope. This rope is cleaned, cut, cooked, and bleached, in much the same way as rags are treated.

CORNSTALK

The utilization of cornstalk pulp for paper has been suggested many times. Moreover, no small amount of experimentation has been carried on, and numerous patents have been granted covering methods of manufacturing cornstalk paper. To date, however, no commercial unit has actually been set up for such manufacture, though at least one company is making board from this material.

Figure 15.-Storage of raw straw for the making of strawboard. Each bale of straw makes approximately 50

pounds of board.

Figure 16.-Storage of waste paper for paper making. Over $40,000,000 worth of waste paper was used last year in the manufacture of numerous types of paper and paperboard.

COTTON LINTER

Cotton linters are used for special pulps, such as those required by the rayon and plastics industries; but even in these fields the use of wood pulp is heavy.

WASTE PAPER

Enormous quantities of waste paper are pulped annually in the manufacture of paper and paperboard. Census figures show that for the year 1935 over 3,500,000 tons of paper stock valued at over $40,000,000 were consumed by our domestic industry. Paper stock is used in the manufacture of container board, boxboards for folding and set-up boxes, wallboard, and papier mâché, and in the manufacture of toilet tissue, towels, book paper, and numerous other items. The percentage of waste-paper pulp used in mixture with virgin pulp may range from a very small to a very large figure.

We are all familiar with the collector, often the junkman, who buys. our waste paper, both at home and at the office. After collection, the papers must be sorted and baled before being sold to the paper mill. Newspapers must be separated from heavy book and magazine papers, from kraft papers, from container manilas, and other papers (though there are several grades containing mixed papers), for the mill must know just what type of stock it is starting with. The prices paid for waste papers vary with the grades and also with the law of supply and demand.

On being received at the mill, the papers are further sorted, all dust and dirt is removed from them and they are shredded to a size that will quickly absorb the cooking solution. Caustic soda and soda ash (sometimes one, sometimes both) are used in this solution. After cooking, the stock is washed and bleached.

MANUFACTURE OF PAPER

The manufacture of paper is usually conceded to begin with the beating and refining of the pulp.

BEATING AND REFINING

Beating and Jordaning are distinct mechanical operations. Both have for their purpose the preparing of the pulp so that it will mat or felt well when being formed into the sheet on the paper machine. The two operations are carried on successively. They not only reduce the pulp to its individual fibers, but they also broom, split, and otherwise cut these fibers. A gelatinous effect commonly referred to as "hydration" also takes place on the exterior of the fiber during beating and this gelatinization assists in binding the fibers together in the paper sheet. With some types of paper, as with newsprint, the amount of beating is slight. With most papers, however, particularly the quality papers, the beating operation is one of the most important steps in the manufacturing process.

Beating is usually done in the hollander type of beater. This beater was introduced into the United States paper industry about the middle of the eighteenth century. It comprises, fundamentally, an oblong-shaped open tub with rounded ends, which carries a partition

Paper and Allied Products (1935), issued by Bureau of the Census, U. S. Department of Commerce, Washington, D. C.

or midboard down the center parallel with the longitudinal sides. (See fig. 17.) The partition does not, however, extend the whole length of the tub but stops off from each end at a distance approximately one-half the tub width. Thus, during the beating process, the pulp mixture can flow continuously down one side of the tub, around the end, back the other side and around the other end. As the pulp mass moves through this channel along one side of the beater, it must pass under a heavy roll, mounted crosswise of the tub and fitted with metal bars. This roll turns past a bedplate similarly fitted. It is in passing between these two sets of bars that the cutting, broom

Figure 17.-A beater (experimental size). The pulp mass seen in the foreground flows slowly around the tub in its course to or from the roll. The roll adjustment is seen in front of the operator, and the washing cylinder is on the opposite side of the tub.

ing, and splitting are largely accomplished. Color, sizing, and other nonfibrous materials are often added in the beater.

Beating, when done, is nearly always a "batch" operation. Usually several beaters operate to supply one paper machine; and as each beater prepares its batch of pulp, the beaten batch is dumped into a storage chest, from which it is continuously pumped to the Jordan.

One or more Jordans may be used with each paper machine. The treatment and handling of the pulp mixture is a continuous operation. The Jordan further reduces and prepares the pulp as it is received from the storage chest and passes it through to the paper machine. In mills making tonnage grades, such as newsprint and kraft papers, the beating operation is frequently dispensed with; then the whole pulp-reduction operation is accomplished in the Jordan.

LOADING, SIZING, AND COLORING

The three operations of loading, sizing, and coloring are treated together, since they are all largely done at the beater. Load, size, and color are added to make the sheet more serviceable than it would be if merely of fibers, and in most cases the three operations follow one another in the order named.

LOADING

By loading is meant that a mineral filler is added to the sheet. The chalk, talc, clay, or other mineral substance is mixed in with the pulp mixture at the beater, and the whole is carried on through to the paper machine. In the finished sheet the mineral fills in and levels off what would otherwise be tiny interstices between fibers and makes for a smoother surface. The largest quantities of filler are added to the book papers, where they give an opaque sheet of good ink-absorbing qualities, and one that will take fine line cuts and halftones well. Filler is also added to a number of special paper products, such as photographic paper and stereomatrix board. It should be made clear, however, that many papers are not given a "load" or a filler at all. Greaseproof paper, vegetable parchment, glassine, waxed tissue, and similar nonopaque papers carry no filler; neither do many of the ledger and bond papers.

SIZING

Sizing is the treatment given to the furnish (pulp mixture) or to the paper sheet to make the fiber resistant to the penetration of water or ink. Thus, a sized paper can be written on without the spreading or feathering of the ink. With engine sizing, the size, usually a compound of rosin in the form of rosin soap, is dissolved and mixed with the pulp and water in the beater, in much the same manner as might be done with any other soap. When the solution is evenly distributed throughout the batch, alum is mixed in, and the resulting millions of tiny curds of rosin and alumina more or less. encase the individual wood fibers throughout the batch. In the sheet, the heat of the dryers and the pressure of the calender rolls dry and give even distribution of the rosin over the surfaces. For special papers, various other chemicals are often added-for example, in cigarette paper, where continued burning is desired.

Some types of paper are tub-sized after the sheet has been formed and dried. The fibers of the sheet may have been previously enginesized in the beater, as above described. In either case, the tub-sizing treatment is given the finished paper sheet by running it through a tub or vat of the size and subsequently redrying it. Tub-sizing is, in effect, a surface-sizing operation. Animal glue, starch, gelatin, or casein is customarily used as the sizing material.

COLORING

Coloring is largely done in the beater and is therefore a fibercoloring operation. There are, however, several sheet-coloring methods used-as, for instance, calender coloring and tub coloring. For the coloring of paper, analine dyes are now used much more than are either the pigments or the natural organic dyes. These dyes are preferred largely because of the broad range of shades possible, because they do not effect the strength of the sheet, and because they are usually the cheapest.