Beating.—Beating is that operation concerning which the paper makers often say "there is where the paper is really made," and although the statement may not be literally true it contains a great deal of truth. It is the operation whereby the fibers are separated from each other, reduced to the proper lengths, and put in such a physical or chemical condition that they felt properly and form into a satisfactory sheet. It is probable that the quality of the sheet depends more upon the proper beater action than upon any other single operation. The action consists in drawing a water suspension of the fiber between two sets of rather blunt knives, one set being [ -16- ]located in the bottom of a circulating trough and the other set on the periphery of a roll revolving just above the former set of knives. It is during this operation that the loading and sizing agents are incorporated and the whole furnish is tinted either to produce a satisfactory white or the desired color.
The term "paper making," as used in this publication, means the operation of forming the finished sheet of paper from stock which has been furnished and prepared in the beater. In these tests a 30-inch Fourdrinier machine of regular construction was used, a machine which often is used for the production of paper for filling regular commercial orders. The machine is designed to cause the water suspension of fibers to flow on to a traveling wire cloth, whereby the water drains away. More water is removed by passing the wet sheet through a series of press rolls, after which the sheet is dried on steam-heated drums and passed through polished iron rolls, which impart a finish to the sheet. A Jordan refining machine was employed in conjunction with the machine to improve further the quality of the fiber, and a pulp screen was used in order to remove coarse and extraneous materials from the fiber.
DESCRIPTION OF TESTS.
The nature of each complete paper test and the dependence of each operation on the others were such that it does not seem advisable to submit the results of the seven tests in tabular form. The numerous cooks, however, which furnished the pulp for the paper tests are presented in Table I in all essential detail.
TABLE I.—Data on cooking hemp hurds.
| Cook No. | Caustic soda used (percentage of bone-dry hurds). | Strength of caustic soda (grams per liter). | Causticity of soda solution. | Cooking | Yield of bone-dry fiber (percentage ofbone-dry unsieved hurds). | |
| Time (hours). | Temperature(°C.) | |||||
| 293 | 20.6 | 100 | 75.3 | 3 | 166 | |
| 294 | 21 | 100 | 75.3 | 3 | 166 | |
| 295 | 21.6 | 100 | 75.3 | 3 | 166 | |
| 296 | 20.3 | 100 | 75.3 | 3 | 166 | |
| 301 | 21.9 | 100 | 82.5 | 4 | 166 | [3] |
| 302 | 24.4 | 100 | 82.5 | 4 | 166 | |
| 303 | 24.2 | 100 | 84.3 | 4 | 166 | 44.1 |
| 304 | 25 | 100 | 84.3 | 4 | 170 | 39.5 |
| 305 | 25 | 100 | 84.3 | 5 | 170 | 39.4 |
| 306 | 27.8 | 107.5 | 84.3 | 4 | 166 | 36.5 |
| 307 | 26.7 | 107 | 84.4 | 5 | 170 | 38.1 |
| 308 | 26 | 107 | 84.4 | 5 | 170 | } 37.3 |
| 309 | 27.3 | 107 | 84.4 | 5 | 170 | |
| 310 | 27.1 | 107 | 84.4 | 6 | 170 | 37.0 |
| 311 | 27.2 | 107 | 84.4 | 6 | 170 | 36.8 |
| 312 | 28.3 | 116.5 | 85.5 | 5 | 170 | 35.9 |
| 313 | 29.1 | 113.1 | 84.9 | 5 | 170 | }35.2 |
| 314 | 29.1 | 109 | 83.9 | 5 | 170 | |
| 315 | 29.4 | 109 | 83.9 | 5 | 170 | 34.9 |
| 316 | 30 | 109.5 | 84.9 | 5 | 170 | 37.2 |
| 317 | 29.6 | 109.5 | 84.9 | 5 | 170 | 37.0 |
| 318 | 29.6 | 107 | 84.8 | 5 | 170 | 37.7 |
| 319 | 29.4 | 107.5 | 84.2 | 5 | 170 | }35.4 |
| 320 | 29.3 | 107.5 | 84.2 | 5 | 170 | |
[ -17- ]Discussion of the various cooks will be given in connection with the descriptions of those paper tests in which the stocks from the cooks were used, since a stock and its cooking condition can be judged adequately only after it has been put through the various processes and into the finished sheet of paper.
The first test consisted in making four separate cooks, Nos. 293, 294, 295, and 296, of approximately 300 pounds each, dividing the total stock into two parts and making two separate paper tests. The first test was made primarily in order to learn some of the qualities and characteristics of the stock and to get the machinery equipment adjusted properly. The yield of fiber was not determined in this preliminary test, since the knowledge of it was not essential at this stage of the work. The cooked stock which was emptied into the drainer to be washed free from black liquor was composed largely of whole pieces of hurds, but only slight pressure between the fingers was required to crush the pieces. In the case of wood, this condition ordinarily would indicate undercooking, but might not in the case of hurds. Further observation on the action of the cooked stock during subsequent processes was necessary in order to judge of its quality or the suitability of the cooking conditions. The total cooked stock, about 500 pounds, was divided into two portions of 200 and 300 pounds, respectively, and work was continued on them separately. The 200-pound test, designated as run No. 135, was put into a 350-pound washing engine, washed one hour, and given a total light brush of 2¼ hours. The washing removed a great amount of dirt, but the engine did not reduce the hurd stock as much as was desired. After heating the stock in the beater to 40° C., it was bleached with bleaching-powder solution, 94 gallons at 0.418 pound bleach per gallon, equivalent to 19.7 per cent of the fiber. This percentage of bleach is regarded as too high for stock intended for book-paper manufacture, and subsequent cooks therefore were given harder treatment in order to reduce this figure. After draining and washing free from bleach residues, the stock was furnished in the beater with 13 per cent of clay, 1 per cent of resin size, and 2.5 per cent of alum, was tinted blue, given one hour's light brush, and pumped to the stock chest. When running it on the paper machine, the Jordan refiner seemed to have little effect in reducing shives of undertreated wood, which indicated further the necessity of harder cooking. The furnish acted well on the paper machine at 70 feet per minute, but appeared somewhat too "free" on the wire. The paper produced from this test is of very low quality, due to the improper preparation of the stock, lack of sufficient bleach, the use of too small an amount of blue tinting, and the presence of an excessive amount of dirt, sand, and shives. The excessive amount of dirt and sand suggested the sieving of the hurds before cooking, and this was performed in all subsequent cooks.[ -18- ] The finish of the sheet is very poor, due to the fact that the calender stack was composed of very light rolls which did not have a satisfactory surface, yet the stack is known to be able to produce better finishes if the proper stock is employed.
Run No. 136 was made on the 300-pound portion of stock from cooks Nos. 293, 294, 295, and 296, and in essentially the same manner as run No. 135. The stock was washed one hour, but given a brush of three hours, and this brush was harder than in run No. 135. Bleach to the extent of 19.8 per cent of the fiber was used, assisted by 1 pint of oil of vitriol, and the resulting color was an improvement over that of run No. 135. After adding 13.5 per cent of clay and sizing with 1.1 per cent of resin size, the furnish was given one-half hour's light brush, tinted, and run on the machine, which was set at 70 feet per minute. This stock acted better on the wire and gave no trouble on the machine, but it still seemed to be impossible to reduce the wood shives by manipulation of the Jordan refiner. The resulting sheet is an improvement over that produced by No. 135, but is far from satisfactory.
Run No. 138 was made from hurds which, as in all subsequent tests, were sieved on a 11½-mesh wire screen until practically all the loose dirt and sand was removed, which operation caused a loss averaging 3 per cent of the hurds. Stock from cooks Nos. 302 and 303 was used for this run and the increased amount of caustic soda and the increase in the time of cooking gave a stock of better appearance than those of preceding tests.