HEMP HTJEDS AS PAPER-MAKII^G MATEEIAL. 23 



against possibly six to eight hours; 11.5 per cent bleach as against 

 8 to 10 per cent. Thus, it is evident that the cooking conditions 

 employed were sHghtly more severe and expensive than those in 

 commercial use with poplar wood. 



The yield of total fiber obtained from the hurds may be placed at 

 35 per cent of bone-dry fiber calculated on the bone-dry weight of 

 hurds used, or 33.1 per cent of air-dry fiber calculated on air-dry 

 hurds. The yield of bleached fiber was not determined in this pre- 

 liminary work, but may be safely estimated as 30 per cent, which is 

 low when compared with a yield of about 47 per cent of bone-dry 

 bleached fiber from bone-dry poplar wood. It is believed quite 

 possible that satisfactory cooking conditions may be found which will 

 give a higher yield than was obtained during these tests. The stock 

 should be classed as easy bleaching, and 11.4 per cent of bleach is a 

 satisfactory figure, although a httle high. 



As to beating cost, in the last two and most satisfactory tests the 

 total washing and beating time was three hours, which may be about 

 an hour more than ordinarily is used in making papers of this grade, 

 although the practice varies to a considerable extent. 



In regard to furnish, there is such a diversity of practice that it is 

 difficult to make a comparison, but if the hurd stock can be produced 

 as cheaply as soda-poplar stock, the furnish used in these last two 

 tests should be regarded as satisfactory to the book and printing 

 paper manufacturer. 



The finish of the paper was not all that might be desired, but that 

 was due almost entirely to the calender stack available for the work, 

 which was composed of nine hght roUs, many of which were about 

 6 inches in diameter and which had not been reground for some time. 

 From a small test on a large calender stack it was readily shown that 

 the paper produced is capable of taking a satisfactory finish. 



This comparison, satisfactory in many respects, develops two 

 factors which are decidedly unfavorable to hemp hurds, namely, raw- 

 material storage and digester capacity, and they must be taken into 

 full account in considering the paper-making value of this material, 

 although it should be recognized that investigation may result in the 

 material improvement of these conditions. Moreover, it is not at all 

 improbable that further investigation would develop more satisfac- 

 tory treating conditions and more suitable furnish compositions, and 

 the belief in this possibility is strengthened by the fact that material 

 progress was being made at the conclusion of this preliminary work. 



Calculations on the raw material and acreage for a permanent sup- 

 ply for a pulp mill producing 25 tons of fiber a day for 300 days per 

 annum, or 7,500 tons per annum, give the comparison between hurds 

 and wood shown in Table II. 



