Critical study of methods of measuring the bulk of paper
F.T. Carson · Bureau of Standards Journal of Research · 1929
Because of the prevalence in the paper industry of diverse methods of measur- ing the property of bulk or voluminousness of paper, a study has been made of methods commonly used, and as a result of this investigation a standard method is proposed for measuring bulk.It was found that the different pressures used in the variable-pressure type of apparatus, and the use of an insufficient number of sheets in the case of measurements with thickness gages, are chiefly re- sponsible for the diversity of results ordinarily obtained.As a result of com- parative tests made on different types of apparatus and at various pressures, it was found possible to select procedures for the two most commonly used meas- uring devices so as to bring them into substantial agreement with each other and with the bulk actually obtaining in bound volumes.A standard procedure is recommended which permits either the measurement of a pack of paper 0.1 inch or more in thickness with a thickness gage of standard type or the measurement of a 1-inch pack under a pressure of 5 lbs./m. 2 by means of a pressure bulker.It is recommended that the results be expressed as (a) bulking thickness, or the thickness in hundredths of an inch of a 100-sheet pack; and (b) specific bulk, or the ratio of bulking thickness to the standard ream weight of the paper measured.