Ask A Scientist General Science Archive

name         Kendle S.
status       student
age          16

Question -   Why do Listerine breath strips, when held in the palm of
your hand, curl up in one direction on one side, and curl in the other
direction when flipped to the other side?  (The strip is rectangular, and
curls up the long way on one side, and curls along the short side when
flipped the other way.)
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It is absorbing moisture unequally from each side.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy
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Kendle,

Very likely, the strips are made of two layers whose grain runs crosswise to
each other. Heat and/or moisture from your hand causes the strip to curl
along the grain pattern of the side that's touching your hand.

Regards,
ProfHoff 420
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One side of the strip must have a coating that is different than the
other side. The two sides have a different coefficient of expansion, either
with respect to the temperature, or with respect to the moisture content. I
suspect the difference is a difference due to moisture absorbency of one
side vs. the other.

Vince Calder
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