Chemistry of pulp and paper making . Fig. 52. District of Columbia Paper Tester 4o6 PAPER TESTING t^pe, in which the paper is clamped against a rubber diaphragm,through which the pressure is applied to a circular area of thepaper measuring one square inch. The Mullen tester, Fig. 51,and the District of Columbia paper tester. Fig. 52, are of thehydrauKc type. The second type of bursting strength apparatusis of the spring operated metal plunger design, in which thepaper is clamped between annular rings, through which a springoperated plunger is forced. The Ashcroft tester, Fig. 53, is theonly on
Chemistry of pulp and paper making . Fig. 52. District of Columbia Paper Tester 4o6 PAPER TESTING t^pe, in which the paper is clamped against a rubber diaphragm,through which the pressure is applied to a circular area of thepaper measuring one square inch. The Mullen tester, Fig. 51,and the District of Columbia paper tester. Fig. 52, are of thehydrauKc type. The second type of bursting strength apparatusis of the spring operated metal plunger design, in which thepaper is clamped between annular rings, through which a springoperated plunger is forced. The Ashcroft tester, Fig. 53, is theonly one of the above type now on the Fig. S3. Ashcroft Tester The bursting strength to be of greatest use must be expressedin terms of the weight of the sample. This ratio of strengthto weight may then be directly compared with the strength ratioof any other paper, if the same standard size sheet is used ineach case. The strength ratio is expressed as a percentage. Strength ratio = Bursting strength X 100 Weight in pounds (on a size 25 X 40,500) Folding Endurance. The folding endurance of a paper ismeasured by a machine in which a strip of paper is caused to FOLDING ENDURANCE 407 fold back and forth upon itself until it is worn through. TheSchopper Folding Machine, which is the only device so far
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1920
