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Measuring paper wetting processes with laser transmission

Timo Karppinen, Ivan Kassamakov, Edward Hæggström and Jyrki Stor-Pellinen

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We introduce a method to measure paper wetting based on the measurement of monochromatic (670 nm) light transmission through paper. The samples were 49.8–51.7 g m−2 handsheets, the hydrophobicity of which was tuned by the fibre content of the furnish. In addition, one of the samples was internally sized. Impact wetting with isopropanol and water mist pulses was applied. The duration of a pulse was 100 ms, and the amount of liquid per pulse was 12.6 ± 1.2 g m−2. Optical changes in a paper sample were detected by measuring the average intensity of transmitted light through a selected area. The results showed that different wetting processes (pure capillary and combined capillary and diffusion wetting) could be distinguished from each other. With the presented method, differences in the individual behaviour of the samples during wetting could also be seen.


PACS

42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

78.20.-e Optical properties of bulk materials and thin films

42.25.Bs Wave propagation, transmission and absorption

68.08.Bc Wetting

68.35.Fx Diffusion; interface formation

Subjects

Soft matter, liquids and polymers

Condensed matter: electrical, magnetic and optical

Instrumentation and measurement

Surfaces, interfaces and thin films

Optics, quantum optics and lasers

Dates

Issue 7 (July 2004)

Received 5 March 2004

Published 28 May 2004



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