20 BULLETIN 322, U. S. DEPARTMENT OF AGRICULTURE. 



Fiber-board manufacturers would do well to pay more attention to 

 the reaction of their waste liquors. A few drops of 1 per cent phe- 

 nolphthalein in 50 per cent alcohol dropped into about a quarter of an 

 ounce of the waste liquor should produce an intense red color at once. 



MILL TESTS ON THE MANUFACTURE OF FIBER BOARD. 



Fiber-board mill tests were again undertaken in a fiber-board mill 

 in Maine, but flax tow was used instead of the straw that was 

 emploj^ed in the previous work. The regular machines were used 

 in all of these tests and the work was performed by the regular mill 

 empkryees; in other words, the flax tow was subjected to actual com- 

 mercial manufacturing conditions, although in some of the tests 

 slight changes in procedure were made, as will be shown. 



Bleach No. 23^. — A charge of 4,062 pounds was treated with 14.6 

 per cent of burned lime by slaking 578 pounds of the lime in 1,600 

 gallons of water in the bleach boiler, then adding the charge of tow. 

 Direct steam was admitted, and the pressure was brought up to 110 

 pounds in 3 hours and maintained for 4 hours, after which the 

 pressure was relieved in 2 hours and the charge dumped. 



After remaining on the drain floor over night this stock was 

 made into a 500-pound beater furnish of one-third flax tow, one- 

 third mixed strings, and one-third board cuttings, in the following 

 manner : The mixture of tow and mixed string was washed in the 

 beater for 2 hours, when the board cuttings and sulphite screenings 

 were added and the charge beaten off in a total of 12 hours. Near 

 the end of the beating, the filler, color, and size were added. This 

 stock was run over a 44-inch wet machine, loft dried, and put 

 through the board calenders. The wet boards from the wet ma- 

 chines measured 38 by 44 inches, and after they were dried and 

 calendered they measured 33 by 44 inches, which is about the correct 

 amount of shrinkage. These boards were sold in the trade, but not 

 as counter boards, as they were too brittle for that grade. The 

 brittleness was due, according to the management and employees, 

 to the fact that the stock was beaten too short. In working with 

 any new material, its characteristics and differences must be learned 

 before its full possibilities can be developed, and many failures must 

 be expected during the earlier stages of development. 



Bleach No. 235. — This bleach was made in the same manner as 

 No. 234, but 15 per cent of lime was used and the charge cooked 

 at a steam pressure of 75 pounds for 9 hours, the total time of cook- 

 ing being 12 hours. The stock from this bleach was used in the 

 same furnish and manner as that of bleach No. 234. This furnish 

 was beaten off in a total of 12 hours, loaded, colored, and sized, as in 

 the previous test. The stock showed up very well in going over the 

 wet machine, giving a board measuring 38 by 44 inches wet, which 

 after loft drying and calendering measured 33 by 44 inches. This 



