PAPER 



beating operation. In the beater 

 the half-stuff is reduced to a con- 

 dition of ultimate fibre, by the 

 complete separation of each in- 

 dividual fibre, which is also re- 

 duced to suitable lengths. At the 

 same time certain properties are 

 imparted to the stock, dependent 

 upon the length of time the pulp 

 remains in the engine, and the 

 manner of treatment it receives. 



Treatment of the Pull 



The modern Hollander type 

 beater is an oblong trough about 

 half as wide as it is long, semi- 

 circular at the ends, with a short, 

 central partition, called a mid- 

 feather. The beater roll which cir- 

 culates the pulp is provided with 

 blades, which may be of steel or 

 bronze, placed hi clumps round the 

 circumference. Directly under the 

 roll is a bed-plate also fitted with 

 blades or bars. The bedplate is set 

 at a slight angle with the face of 

 the roll, in order that a cutting 

 action may be obtained, and its 

 surface takes up the curvature of 

 the roll. It is by manipulation of 

 this roll that the beating opera- 

 ation is performed. The time re- 

 quired may vary from 1 to 16 hours 

 according to the material and type 

 of paper required. The roll usually 

 revolves with a peripheral speed of 

 2,000 ft. per minute. 



The diluted paper pulp is 

 screened and made into paper, 

 one sheet at a time, by the vatman, 

 who dips a shallow sieve, in the 

 form of a hand mould, into a vat of 

 the pulp, withdraws it with a 

 definite charge of stuff, and almost 

 simultaneously shakes the mould 

 in a peculiar fashion, in order that 

 the individual fibres shall felt or 

 interlace as the water falls through 

 the sieve. The wet sheet is drained 

 and placed by the " coucher " 

 between damp woollen felts, 

 which are piled, and later sub- 

 mitted to great pressure in an 

 hydraulic press. After the excess 

 water is removed, the sheets are 

 taken out and air dried. The dry 

 sheet is sized by dipping into a 

 solution of gelatin size, then again 

 air dried. The paper is surfaced by 

 placing each single sheet between 

 two zinc or copper plates, and 

 passing a pile of these through 

 heavy calender rolls, which opera- 

 tion is called plate glazing. 



Half-stuff produced from rags 

 is practically pure cellulose. When 

 other raw materials are used, 

 different chemical processes may 

 be employed to eliminate the non- 

 fibrous and non-cellulose elements 

 prior to the beating operation. 



Chemical pulp is produced by 

 the soda, sulphate or sulphite pro- 

 cess, and the names given to the 

 resultant pulp indicate the mode 



5960 



of its preparation. Thus : soda 

 pulp from digestion with caustic 

 soda ; sulphate from digestion with 

 a mixture of caustic soda and sul- 

 phite of soda ; and sulphite from 

 digestion with bi-sulphite of lime 

 and magnesia, containing a certain 

 percentage of free sulphur-dioxide 

 in solution. Chemical wood pulp 

 carefully prepared is the best sub- 

 stitute for rags. It is difficult to say 

 in what paper it cannot be applied. 

 Ground wood, or mechanical 

 pulp, is, as the name denotes, pre- 

 pared solely by mechanical means. 

 Wood blocks, previously barked 

 and cut into suitable lengths, are 

 pressed by hydraulic pressure 

 against grooved revolving cylind- 

 rical stones. A stream of water 

 directed between the blocks carries 

 away the ground pulp, which con- 

 sists of microscopic splinters con- 

 taining all the ingredients of the 

 growing timber. Ground wood is 

 only used in the manufacture of 

 paper having a transitory value, 

 as news paper, of which it is the 

 chief constituent. 



The Beating Process 

 The production of chemical wood 

 pulp and ground wood is usually 

 carried on at pulp mills located 

 near the forests, and situated where 

 water power is available. In the 

 countries where pulp mills are 

 adjacent to, or part of the paper 

 mills, both chemical pulp and 

 ground wood are used for paper 

 manufacture in the slush state, but 

 they require to be manufactured 

 into sheet form when shipped to 

 other markets. Mechanical pulp is 

 usually shipped 40 to 50 p.c. 

 moist, and chemical pulp air dry. 

 For paper other than newsprint, 

 all materials after reaching the 

 half-stuff stage require treatment 

 in the beater before they are ready 

 to pass on to the machine. During 

 the beating process, colouring, 

 filling, and sizing materials are 

 added to the stock. Resin soap and 

 alum are the chief sizing materials 

 used. After beating, the stock is 

 passed through a refining machine. 

 Diluted to less than 1 p.c., it is 

 next pumped into the strainers, 

 which consist of flat or rotating 

 screens fitted with plates perforated 

 with very fine slits, about 7/l,OOOths 

 of an inch in width. The liquid 

 pulp now flows over the apron, 

 under a sluice, called a " slice," 

 and on to the wire of the paper 

 machine. The wire is an endless 

 sieve travelling at any speed up to 

 1,000 ft. per minute, according to 

 the quality of the paper being made. 

 The moment the pulp comes under 

 the influence of its forward move- 

 ment, felting of the fibres is brought 

 about by a lateral shake imparted 

 to the wire by mechanical means. 



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Endless rubber belts, called " deckle 

 straps," travelling on the top and 

 at each side of the wire, prevent 

 the pulp overflowing the sides. 



As the pulp travels forward, the 

 fibres settle down in position, 

 parting with the water through the 

 wire. Passing over vacuum boxes 

 more water is extracted, and still 

 more by the pressure of the couch 

 roll. Unsupported for the first time, 

 the wet web is carried forward to 

 the press rolls by felts. The function 

 of the presses is to remove still 

 more water, and to smooth out the 

 rough surfaces. The web, now con- 

 taining about 66 p.c. of moisture, is 

 carried to the drying cylinders, 

 which are heated with steam, and 

 conducted to the other end of the 

 machine, where it passes through 

 calender rolls to give a uniform 

 finish on both sides of the paper. 

 If the paper is required on reels, 

 it is usually re-reeled on special 

 machines. 



Watermarks are obtained in 

 hand-made p_apers by means of a 

 raised pattern on the surface of 

 the wire of the mould. The same 

 effect is obtained on the paper 

 machine by using a revolving 

 skeleton cylinder, called the dandy 

 roll, covered externally with fine 

 wire cloth, to which is fixed the 

 design required. This roll revolves 

 upon the wet pulp just before it 

 experiences the full effect of the 

 vacuum boxes. 



Facts and Figures 



The modern paper machine is a 

 very large manufacturing unit, 

 costly, imposing, and ingenious. 

 A machine of the kind illustrated 

 can produce from 1*5 to 2'0 tons of 

 paper per hour. 



There are unlimited varieties of 

 paper, from bank-note paper down 

 to common wrappings. The best 

 and most durable machine-made 

 papers are made from rags, pre- 

 paratory treatment being identical 

 with that pursued for hand-made 

 qualities. 



In 1921 there were in Great Britain 

 and Ireland 260 paper mills, con- 

 taining 568 machines. The world's 

 consumption of paper was estim- 

 ated, in 1912, to be about 9 million 

 tons. The consumption in 1920 

 was probably not less than 14 

 million tons. 



Bibliography. Chapters on Paper 

 Making, C. Beadle, 1904-7 ; The 

 Paper Trade, A. Dykes Spicer, 1907 ; 

 Paper and itsUses.E. A.Dawe, 1914 ; 

 The Paper Mill Chemist, H. P. 

 Stevons, 2nd ed. 1919; Paper 

 Technology, R. W. Sindall, Srded. 

 1 920 ; Modern Paper Machinery, G. 

 S. Whitham, 1920; Chemistry of 

 Pulp and Paper Making, E. Suter- 

 meister, 1920 ; Text, Book of Paper 

 Making, C. F. Cross and E. J. Bevan, 

 5th ed. 1921. 





