Eur. Phys. J. Appl. Phys.
Volume 32, Number 1, October 2005
|Page(s)||65 - 71|
|Section||Instrumentation and Metrology|
|Published online||25 October 2005|
Measuring liquid penetration in the thickness direction of paper
Department of Physical Sciences, University of Helsinki, PO Box 64,
00014, Helsinki, Finland
2 Helsinki Institute of Physics, PO Box 64, 00014, Helsinki, Finland
3 Oy Keskuslaboratorio - Centrallaboratorium Ab, PO Box 70, 02151, Espoo, Finland
Corresponding author: email@example.com
Revised: 25 May 2005
Accepted: 24 June 2005
Published online: 25 October 2005
We introduce a method to measure liquid absorption into paper based on measuring white light reflected from it. The method was used with 49.8–51.7 g/m2 pilot papers, whose hydrophobicity was tuned by their fiber content and furnish. In addition, one of the samples was internally sized. Impact wetting was used where a droplet of mineral oil, isopropanol or deionized water was applied to the paper surface opposite to the one facing the monitor. The volume of liquid per droplet was (0.9±0.2) μl to (1.3±0.1) μl. The sample was illuminated with an ordinary 20 W light bulb from above. The light intensity reflected off the sample was recorded with a fast charge-coupled camera during the liquid penetration. Optical changes in the paper sample were studied by calculating the average intensity of the reflected light from a selected area. The results showed that the speed of pore wetting, mainly in the z-direction, could be measured with each liquid-sample combination. Hence a digital camera based light reflection measurement can provide information about thickness direction liquid transport in paper.
PACS: 47.55.Mh – Flows through porous media
© EDP Sciences, 2005
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