Timbers. 



98 



[Feb. 1907. 



that the water used shall be pure and free from suspended solid bodies, sand or clay- 

 being particularly objectionable, as they cling to the pulp and affect it considerably 

 when it gets into the paper maker's hands. It is, therefore of course, highly necess- 

 ary that in establishing the sites for a pulp-making centre, there shall be a suitable 

 water supply, otherwise the water used for grinding must be carefully filtered, and 

 in some mills where the water is not all that could be desired the water, after it 

 has passed through the sorting screens, is collected, filtered, and again used. 



SORTING PULP, 



which follows the grinding, is a very important detail. The sorter is, in fact, a kind 

 of sieve or series of sieves, and Voith's shaking sieve is probably one of the best 

 types in use, The frame rests on steel springs, and the cranked axle, by an ingenious 

 arrangement, secures uniform running, whilst the sieves jerk and shake rapidly, 

 400-500 motions per minute. The application of springs reduces the wear and teat- 

 very materially, and also minimises the noise. The particles of brown wood, having 

 thus been mechanically sorted, the pulp is conducted to the settling vats, the 

 dehydrating apparatus, or the board machines, as may be desired. There are 

 various processes for dealing with the particles of wood which do not pass through 

 the sieve, and, generally speaking, it may be said that they are reground and again 

 passed through a fine meshed sieve. 



The removal of water from pulp is a very important element, which has 

 to be taken into consideration, especially where the question of freight has to be 

 considered ; and as a considerable quantity of pulp has to be shipped over large dis- 

 tances, it is obvious that it is not desirable to carry more water in the pulp than 

 circumstances necessitate. Therefore, the importance of this is a matter which has 

 a considerable bearing on the immediate advantage which accrues to a mill in the 

 position of making up its paper from pulp on the spot, but the full consideration of 

 this subject is a matter which is rather outside the scope of this paper. There are 

 many forms of drying apparatus, and the preparation of perfectly dry pulp is now 

 quite practicable- As bearing upon the importance of selecting wood of the right 

 class for the particular purpose intended, I may here observe that Prof. Winkler 

 made interesting experiments with pulp from different varieties of wood, which were 

 exposed to the action of the air at a temperature of between 30° to 50° F., and he 

 obtained most interesting results, which are fully set out on page 42 of Bersch's book. 



To those of my audience who desire to go thoroughly into the chemistry of 

 paper-making, I can recommend a publication on this subject by R. G. Griffin and 

 A. D. Little, published by Howard, Lock wood & Co., New York. From memory, I 

 believe the book I refer to was published in 1894. It contains a mass of information 

 of a very useful character. Other valuable books to those who desire to go into the 

 matter of wood pulp thoroughly are :—" Vegetable Physiology" (Goodale), also 

 Schubert's " Die Cellulosefabrikation," and amongst our British authorities, the 

 writings of Mr. Clayton Beadle, Messrs. Cross and Bevan, Dr, Stevens, and Mr. R. 

 W, Sindall are amongst the most instructive ; whilst the lectures delivered 

 before this Society not very long ago by my friend, Mr. Julius Hubner, of the Man- 

 chester Technological School, also afford much imformation on the subject of paper 

 making generally, and on the treatment of wood pulp from the paper-maker's point 



of view. 



Crushing. 



Another interesting process in the preparation of mechanical wood pulp was 

 known as the crushing process, and the effect is the preparation of pulp from steamed 

 wood without the necessity of grinding. This has been known as the Rasch-Kirshner 

 method. The steamed wood was first converted into small pieces by means of a 

 chopping machine of special design, and then the wood was cut by a knife mechani- 

 cally driven lengthways into shavings of fixed size, or lengthways as well as cross- 



