140 TEXTILE FIBRES. 



In making paper from wood pulp it is frequently, although not always, 

 ground up with some water into a damp paste. Then this is thrown into 

 a beating engine, in which it is further ground with water into a pulp. 

 While in this engine it is treated with bleaching powder, if necessary, to 

 bleach it, thus imparting to it a good white colour. It is afterwards mixed 

 with China clay and resinous sizes, to give it the qualities of a good 

 paper, and in this condition it is sent' to the paper-making machine. 

 Wood pulp is used chiefly for making paper for newspapers. 



Writing papers and book papers are still made from rags, although 

 in the preparation of some cheap kinds a little wood pulp may be mixed 

 with them. 



Wood-pulp paper deteriorates with age and wear ; it breaks up into 

 small particles or dust. Its spontaneous combustion is very doubtful. 



Formerly it took sixteen hours to make a ton of rags into paper, but 

 at the present time one ton of pulp can be made into paper in an hour 

 and a half. This is mainly due to improvements that have taken place 

 in the processes employed in the manufacture. The bales of wood pulp 

 weigh about 400 Ibs. 



Most paper machines have ordinarily from seven to fourteen cylinders. 

 A machine at a paper mill at Barrow-in-Furness is said to have fifty-two 

 cylinders. On the other hand, in America it is sometimes customary to 

 work a machine with only one cylinder. 



Wood pulp, whether mechanical or chemical, is sold in two forms, viz., 

 moist and dry. The moist pulp contains 55 per cent, of water, while the 

 dry pulp contains 10 per cent, of water, and they are bought and sold as 

 containing those quantities of water or moisture respectively. Wood 

 pulp naturally contains from 8 to 10 per cent, of water, and this is 

 known in the trade as atmospheric moisture. In buying and selling 

 moist pulp, allowance is made to the extent of 10 per cent, for such 

 moisture. Moist pulp is therefore considered to contain 50 per cent, 

 of air-dried pulp, made up of 45 per cent, of pulp and 5 per cent, of 

 atmospheric moisture. 



Parcels of wood pulp often contain more water than the quantities 

 named above, and then they have to be sampled and tested. To carry 

 this out, 2 per cent, of the number of bales are taken and weighed, and 

 from these weights the total weight of the parcel is calculated. Samples 

 are then cut from sheets taken from the top, centre, and bottom of each 

 bale, and in these the percentage of water is ascertained by drying in a 

 hot oven at 212 F. From the results any allowances for excess water 

 in the pulp are calculated. 



