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Monday, June 8, 2015

Paper Barrier Properties: Hercules Size Test

The Hercules Size Test is an instrument flotation test that measures the decrease in reflectance of the side of paper opposite to that which has been covered with a given amount of ink.  The apparatus determines the time required for the reflectance of the sheet surface not in contact with the penetrant (ink) to drop to a predetermined percentage of its original reflectance.

Hercules size tests are more precise than ink flotation tests. Because of its high precision and objectivity, the Hercules size test is widely used as a routing quality control test.  However, the results are influenced by brightness, color, opacity, basis weight, and filler content.  The test should be limited to paper which range in grammage from 50 g/m² to 250 g/m². Procedures have been worked out for making grammage corrections to the test values when different weight papers are to be compared. Lightly-sized papers can give erroneous results if the liquid penetration time is very short.

Other tests designed to measure the sizing of paper include:
  TAPPI T 433, "Water Resistance of Sized Paper and Paperboard (Dry Indicator Method)"
  TAPPI T 441, "Water Absorptiveness of Sized Paper and Paperboard (Cobb Test)"
  TAPPI T 458, "Surface Wettability of Paper (Angle of Contact Method)"
  TAPPI T 491, "Water Immersion Test of Paperboard"
  TAPPI T 558, "Surface Wettability and Absorbency of Sheeted Materials Using an Automated Contact Angle Tester"
  TAPPI UM 481, "Ink Penetration of Paper" (no longer in print)
  TAPPI UM  596, "Water Absorbency of Nonbibulous Paperboard (Water Drop Test)" (no longer published, but available from TAPPI archives)

  • Scott, William & Stanley Tosset, "Properties of Paper: An Introduction", p. 105-106, 1989.
  • TAPPI T 530 om-12, "Size test for paper by ink resistance (Hercules-type method)"