64 BULLETIN 343, U. S. DEPARTMENT OP AGRICULTURE. 



would seem to indicate that almost every sheet is satisfactory to 

 some critic. Some of the comments are as follows: 



Some of the papers, especially Nos. 3 and 6, have beautiful color, but none of the 

 samples are any darker than paper I have seen printed commercially, made from 

 spruce ground wood and hemlock sulphite pulp. * * * 



Personally I like the appearance of sheets Nos. 6, 9, and 10. Of these, I think sheet 

 No. 9 shows up very well. I can not see why any one of these sheets could not be 

 used for printing newspapers. 



I find considerable variation in color when the samples are placed next to each 

 other, but I do not think that the variation is so great that the reader's attention 

 will be called to the color of the paper in any instance. In fact, I have seen many 

 newspapers printed on paper made entirely from spruce wood which did not look 

 nearly so well as the poorest of the samples submitted by you. 



All of these samples on the last run seemed to show up very well indeed, and any 

 one of them ought to serve for newspaper purposes. 



PROBLEMS IN CONNECTION WITH THE EXPERIMENTAL WOODS. 



Some of the woods tested are resinous, which makes them unsuit- 

 able for the manufacture of paper on a high-speed machine. There 

 should be some inexpensive way of treating the resinous woods 

 which would not darken them. It is possible that such treatment 

 would have to be given in the beater. At the same time tests should 

 be made on resinous woods at different times of the year, since it is 

 likely that the time of cutting has a material influence on the opera- 

 tion of the pulp on the paper machine. 



The color of many of the woods could probably be bettered by a 

 suitable bleaching treatment while the pulp was being manufactured 

 into laps or while the latter were being stored. Experiments might 

 also be made to ascertain whether the sheets which are only slightly 

 off color could not be brought up to the standard of white required 

 for news-print purposes by the addition of dyes. 



A problem not directly connected with pulp and paper produc- 

 tion, but of importance to it, is that brought about by the decay 

 of the wood when piled at the mill and of the pulp during storage. 

 Some of the experimental woods decay rapidly and are subject to 

 attacks of insects and fungi. Some reasonably cheap method of 

 insuring these woods against decay and insects will have to be found 

 if they are to be used in any quantity. 



METHODS OF INCREASING THE EFFICIENCY OF GRINDING. 



There are in the United States approximately 1,500 wood-pulp 

 grinders of different sizes, each of which utilizes on the average 350 

 horsepower continuously. The amount of power applied to grinders 

 has been increasing steadily from year to year. Where in the 

 beginning of the mechanical pulp industry 125 horsepower was used 

 on the grinder, in many cases now 600 to 750 horsepower is employed, 

 and in the case of the automatic magazine grinder from 1,000 to 

 1,200 horsepower is utilized. Of the total number of grinders in 

 the United States upon which information is available 36 per cent 



