3.90 OX THE PAPER MANUFACTURE. 



gtlatine, or is conducted between two perforated tubes which saturate 

 both sides of the web as it passes on. In either case, the superfluous 

 size is removed from the web by a pair of copper rollers ; and it is then 

 conducted over a second set of steam cylinders if for printing, or over a 

 set of hot-air drums if for writing. In this country animal size for 

 writing is the rule, although on the Continent of Europe the size in 

 most prevalent use for this class of paper is a well-prepared vegetable 

 size. As a rule, however, the Continental paper-makers use a stronger 

 rag than we do, and, consequently, with careful breaking, capable of 

 carrying a greater quantity of size than a softer material. With us nearly 

 all printing papers are engine-sized. Paper is said to bear well when it 

 resists moderate contact with the tongue ; otherwise it will not stand 

 handling after the process of wetting to which it is subjected in order to 

 prepare it for the printer. If printing papers were only partially dried 

 on the machine, and sent direct over the printing machine without the 

 intermediate process of wetting, the difference in the appearance of the 

 work would be extraordinary ; the effect as demonstrated is that the 

 paper retains its brightness of surface, instead of acquiring the dulness 

 which results from subsequent wetting, and the whole appearance of the 

 printer's work is materially improved ; the practical difficulty would be 

 in determining the weight of water in the paper. 



Judicious bleaching is a very important operation in the manufac- 

 ture of paper. We say judicious ; for if great care be not exercised, the 

 integrity of the fibre is more or less damaged. Rags are prepared for 

 bleaching — 1st, By being cut into small pieces by hand, or sorted by 

 hand and cut by a machine called a chopper ; they are then passed 

 through the duster ; then boiled in a partially caustic alkaline ley, under 

 pressure ; from thence they are conveyed to a breaking engine, where 

 they are washed and broken into the condition of half-stuff — that being 

 an intermediate step between the rag or textile fabric and the stuff or 

 pulp. Having been sufficiently washed, the half-stuff is drained, and is 

 ready for bleaching. Chlorine is the bleaching agent, and is exhibited 

 in two ways, either in combination with lime as chloride of lime, or as 

 gas applied as such. The former is considered the most scientific method 

 of the two, as well as the most economical, although the latter still 

 retains many influential advocates. Thorough boiling is a necessary 

 condition — 1st, In the production of uniform half-stuff ; and, 2nd, To 

 effective bleaching, chlorine being inert in the presence of grease. Com- 

 mon printings, and papers of that class, are usually bleached both 

 expeditiously and roughly. After having been broken in, the rags are 

 retained in the breaking engine, into which is put so many pounds of 

 dry chloride of lime, which becomes thoroughly mixed with the half- 

 stuff by the action of the roll. A little sulphuric acid assists the 

 rapid liberation of the chlorine, and by this means the material acquires 

 a very respectable colour in comparatively a short space of time. This, 

 however, is done at the expense of quality, in every sense of the word. 



