58 Forestry Quarterly 



until 1844 when the German Keller patented the first grinder. All 

 woods can be used for mechanical pulp, although some are pre- 

 ferable. Paper made from this pulp discolors, due to the chemi- 

 cal change in the encrusting substances, lignin, etc., which are re- 

 moved by chemical processes. An improvement, by Cushman of 

 Vermont, cooks the blocks of wood in boiling water to which 

 lime, soda-ash or other chemical agents are added, the grinding 

 then requiring less power and the pulp being of superior quality, 

 especially as regards toughness. 



Common news paper requires about 20 to 30 per cent of chemi- 

 cal pulp, to add the necessary strength, although when, as in Amer- 

 ica, the ground pulp goes directly to the paper machine the felt- 

 ing power is such as to permit even 100 per cent to be used, a 

 point of considerable economic importance. 



Boards for bookbinding, box making, etc., are made of wood 

 pulp ; this being the cheapest material. 



It takes about 90 H.P. to make a ton per day, and can in Can. 

 ada be produced at about $10 per ton dr)^ weight, requiring for a 

 mill producing 3000 tons dry a capital of $100,000 or more. 



The question as to the inventor of the first chemical process for 

 making wood pulp is still not definitely settled. The author de- 

 votes the better part of six pages to a discussion of the contro- 

 versies. Apparently Mitscherlich, (1876), who was professor of 

 chemistry at the forest academy of Miindeu (not Miinchen as the 

 author says), retains the credit of having put the sulphite process 

 on practical basis, although a patent to the American, B. G. 

 Tilghman, in 1867, covered broadly the various chemical pro- 

 cesses. 



Of these there are at least three different in character in prac- 

 tical use, the chemicalsbeingbi-sulphiteof lime, causticsoda, and 

 sulphate of soda, quality and quantity of pulp produced varying 

 with the chemicals. Chemical wood pulp now enters into the 

 manufacture of the highest class papers, and such a degree of ex- 

 cellence has been achieved in this that only an expert could tell 

 the difference between a chemical wood fiber paper and an expen- 

 sive all rag paper. The sulphite process saves, next to the grind- 

 ing process, the largest amount of fiber of best color, the soda 

 process produces a grayish brown pulp in smaller quantity, 

 but is easier to bleach. Of late this process is largely supplanted 

 by the sulphate process, which is cheaper, and in the market is 

 substituted for the soda paper. 



