Wet expansion

Wet expansion, also known as hydroexpansion, is determined as the percentage change in length of a test piece when soaked in water. Pira testing is made in accordance with British Standard BS5879.

Differences in wet expansion across and along the length of a sheet are the result of the alignment of the paper fibres in the grain direction. The wet expansion properties of paper are critical in applications such as books and outdoor posters.

Expert Profile

  • Doug joined Pira in 1989 and has 20 years experience in the physical testing of packaging and packaging materials. He heads a team specialising in packaging and print related technical investigations. In 2004 Doug gained his postgraduate degree with distinction in Packaging Technology from Brunel University.

    Doug Leatherdale
    Doug Leatherdale

    Head of Physical Testing

    Pira International

    +44 1372 80 2108

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