BUBEAU OF PLANT INDUSTBY. 155 



produced, while the sulphate process would not yield apprecial)ly 

 better results than the caustic-soda process. Preliminary tests on the 

 application of the sulphite process, however, give more promise than 

 any process which has yet been tried, but it is a question whether 

 this process could be used in the warmer climates. 



HEMP HURDS. 



During the year 191G it was determined by semicommercial tests 

 that a No. 1 machine-finished printing paper could readily be pro- 

 duced from the waste of the hemp-fiber industry, and Department 

 Bulletin No. 404, " Hemp Hurds as Paper-Making Material," was 

 printed on paper produced from the hurds. 



Because of the scarcity of raw materials for paper making and 

 the increasing tonnage of hemp hurds, the matter was placed before 

 a large paper company, with the result that the entire year's output 

 of a hemp-breaking mill has been contracted for by a commercial 

 firm. The hemp-breaking mill from which this supply of hurds will 

 be obtained is the largest of its kind in the United States and was 

 installed largely as a result of this investigation in 1916. It is 

 anticipated that further expansion in this direction will take i)lace 

 in the next few years. 



FLAX STRAW. 



Considerable time and effort have been devoted to flax straw, 

 the crop waste which aggregates about 1,500,000 tons per annum 

 and is usually burned, with the exception of possibly 100,000 tons 

 w^hich is used in the manufacture of upholstering material and in- 

 sulating boards. 



The curtailment of imports of flax two years ago seriously inter- 

 fered with the production of certain fiber boards and papers, and 

 a great demand for flax fiber arose. Mill demonstrations were 

 made to show that the present commercial grades of domestic flax 

 tow could be used in place of the imported flax. As a result of a 

 demonstration made with a fiber-board company in 1915, in w^hich 

 domestic flax tow was used, this company has used the material since 

 that time, although they state that the practice will have to be dis- 

 continued unless a higher grade of tow can be produced. If this 

 fiber-board market were developed satisfactorily, it would approxi- 

 mate the equivalent of 20,000 tons of flax straw. In 1916 this bureau 

 demonstrated to a container-board company that domestic flax tow 

 could be used in place of foreign fiber, especially if the grade of 

 tow were improved. The potential market for flax in this industry 

 is about 50,000 tons of straw. 



As a direct result of studies in the field, numerous straw-buying 

 stations are now established in northern Minnesota to purchase straw 

 which has hitherto been burned. The possible demand for flax straw 

 for use in the manufacture of fiber board, container board, and 

 cartridge paper would probably approximate 100,000 tons. 



The present low grade of commercial flax tow has been shown to 

 be a serious drawback to the development of its use in the manufacture 

 of paper and boards. This bureau has developed a process of tow 

 manufacture by means of which tows can be produced which are far 



