. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. rate of flow varies with changesin the temperature of the water; this shows diagrammaticallythe viscosity variation of water with temperature. It is veryevident that the less viscous a fluid is the more easily it will passthrough a filtering medium. Instead of waiting for the determination of dry fiber in thesample, the pulp may be diluted immediately, approximatelyto the desired consistency, and the test carried out. The free-ness is corrected later to standard consistency. In order that the results from
. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. rate of flow varies with changesin the temperature of the water; this shows diagrammaticallythe viscosity variation of water with temperature. It is veryevident that the less viscous a fluid is the more easily it will passthrough a filtering medium. Instead of waiting for the determination of dry fiber in thesample, the pulp may be diluted immediately, approximatelyto the desired consistency, and the test carried out. The free-ness is corrected later to standard consistency. In order that the results from the use of these pieces of appara-tus may be reliable, considerable technique must characterize 36 REFINING AND TESTING OF PULP §8 their use in control work. Experience has also shown that theresults they give are comparable only when they are obtained bythe same apparatus and under like conditions; this means thatcomparisons made in different mills, with differences in apparatusand conditions, are not comparable. Ptapam S Sot y V/scos/fy oj PuTi/led Wafer a? Pifferent TempereTures. e —persfi/re, Pefrees CenT/qradeFig. 20. 59. Cleanness or Screening.—An average sample of the pulpis shaken with water, using glass beads if necessary, until it isthoroughly disintegrated; it is then thinned out to about V\consistency, and several sheets are made on an ordinary sheetmachine. The sheets should be sufficiently thin to permit ofexamination by transmitted light. The examination is bestdone by using a set of standards, which consists of a number ofsheets of pulp containing varying amounts of strives, fiber bun-dles, dirt (rust. sand. bark, etc.), from sheets containing butlittle dirt and no shives to sheets containing a large amount ofdirt and shives. the first ranking very high and the second verylow. These sheets are mounted on the glass top of a woodenor metal box. into which are fitted a few electric-light bulbs;when the current is turned on. a strong light will be transmittedth
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1921
