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Angewandte Chemie International Edition 2010, 49,
April 7, 2010
Australia’s plastic bills make life difficult for counterfeiters
Contact: David H. Solomon, University of Melbourne (Australia)
Registered journalists may download the original article here:
Australia's Plastic Banknotes: Fighting Counterfeit Currency
money is the “second oldest profession in the world”—a profession that
truly took off with the introduction of paper money. In order to spoil
things for counterfeiters, Australia introduced the world’s first
banknotes made of plastic in 1988. David H. Solomon at the University of
Melbourne was part of an interdisciplinary team of scientists that
developed these bills. In an essay in the journal Angewandte Chemie,
he and co-author Emma L. Prime trace the technically challenging route
to the development of the plastic banknote.
1966, Australia converted its currency from the British Pound to the
decimal system. The new banknotes distributed by the Reserve Bank of
Australia (RBA) were at the time the most counterfeit-proof bills in the world.
However, it was less than a year before counterfeiters tried to put the
first forged $10 bills into circulation—ingeniously printed on common
office paper. The Governor of the RBA, H.C. (Nugget) Coombs, thus
initiated a project to secure banknotes against counterfeiters.
remembers a photographic expert on the commission, who countered nearly
every suggestion with the words, “if you can see it, you can photograph
it”—meaning that it was always possible to separate the colors of a
banknote, produce printing plates, and forge the bills. “Our idea was to
develop materials that could not be photographed,” reports Solomon,
“which eventually led to the use of clear plastic films as a substrate
in place of paper.” A banknote with a transparent window made of a
plastic film is a simple but highly effective security feature. The
material selected was a polyethylene/polypropylene/polyethylene film.
Two or three of these three-layer films were combined in a hot
lamination process to attain the required thickness of 80 to 90 µm.
security feature is a small picture in the transparent window that is designed
to produce a complex diffraction grating through the diffraction and
interference of light. To protect the diffraction grating and to achieve
the right “feel”, the entire banknote then had to be covered with a
clear polyurethane coating. The team was able to develop a production
process that put everything together in a single run: lamination,
application of white ink, printing the pattern, hot embossing the
diffraction grating, application of the clear coat, and cutting. In
stringent tests, the sample banknotes proved to be more durable than the
paper banknotes in circulation – to such an extent that the higher
production costs were easily balanced out.
1988, the RBA first introduced a limited number of a special $10
banknote for the Australian bicentennial celebration (see picture).
Between 1992 and 1996, the Note Issue Department then replaced all
Australian paper banknotes with plastic ones. “Since that time, other
countries have adopted our technology,” says Solomon. “In Romania, New
Zealand, and Brazil, the counterfeiting rate went down by over 90 % upon
introduction of plastic bills.”