Research on the production of currency paper in the Bureau of Standards experimental paper mill.
M.B. Shaw, G.W. Bicking · Technologic papers of the Bureau of Standards · 1926
The annual replacement of worn-out paper currency in the United States has become of such magnitude as to cause concern regarding the cost of redemption and the limited issue possible with the present printing facilities, which were becoming overtaxed.Increased rapidity of circulation and rougher trade usage are doubtless chiefly responsible for the decreased life of the paper money, but these conditions are unlikely to change in the future.An investigation was, therefore, made to determine the durability factors of paper suit- able for currency use, with a view to increasing the wearing qualities and thereby prolonging the life of the paper money.The experimental tests were made on a semicommercial scale under practical mill conditions.The paper-making fiber was obtained from new linen and cotton rags.Various proportions of these materials were employed, but the best results were obtained with a mixture of 75 per cent linen and 25 per cent cotton.A solution of calcium oxide was used as the boiling liquor in preparing the fiber for the paper-making tests.Bleaching powder (calcium hypochlorite) was employed as the oxidizing agent to remove impurities and whiten the material.Very gradual application of the beater roll pressure reduced to a minimum the reduction in the length of the fibers and by brushing or fraying out their ends insured more and better contacts between adjacent fibers when they were felted in the sheet.The low concentration of pulp in the beater was also a contributing factor in increasing the strength of the paper.The concentration that proved most satisfactory was approximately 3.9 per cent; the beating interval that gave best results was approximately 12 hours.The paper produced was of good printing quality and of much greater fold- ing endurance than that in use at the time of the investigation.The results of the experimental tests have been applied in commercial production, and currency paper double the strength of that previously in use is now being received.It is believed that the data of the investigation will also be of value in the general technic of paper making.