During the course of its deliberations, the committee identified a number of potential ideas that did not warrant full evaluation. As an aid to any future discussions of this topic, these ideas have been identified in tabular form below, together with the reason why they were not taken further.
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Feature Rationale
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Variable edge texture as in coins The thickness of a banknote does not
provide sufficient area for
discrimination, and there is a limited
technical probability of success.
Holes of different shapes Although the principle of holes is
covered in detail, the concept of using
differently shaped holes was rejected
on grounds that, with wear, any shaped
hole will become rounded and will lose
its distinction.
Paper snap or handle Although currency paper has a
distinctive crackle, it was not
considered feasible to provide a range
of sound options.
Different basis weight The committee considered that the range
of basis weight values required to
provide an acceptable discrimination to
the untrained public over six values
would range from tissue paper to board.
Use of superabsorbents The idea of introducing superabsorbent
material that could expand on water
contact and produce localized tactile
marks was considered potentially
useful. However, the idea was rejected,
as it was not considered feasible to
get 100 percent reversibility.
Laminated structures with debonded areas Although considered as an approach to
tactile effect, no technology was
identified that was capable of
introducing this approach.
Variable stiffness The idea of creating different
denominations with different stiffness
was put forward. However, it is well
known that current banknotes vary in
stiffness during the normal circulation
due to wear. It was therefore
considered that this feature would be
very difficult to develop.
Windowed thread as used on English This feature would not be suitable for
currency, with number of windows blind people. It would also require
indicating denomination large-sized windows to assist visually
impaired people. This would not be
possible to achieve on the normal
height of notes and still give adequate
durability.
Laminated sheet with localized punchings From evidence of tactile perception,
on end side with rough center this was considered unrealistic for the
untrained person to identify,
especially where considerations of wear
were taken into account.
Acoustic effect from edge of bill The possibility of each denomination
causing a different sound when dragged
over a surface or blown on the edges
was considered. However, the technology
was considered impractical at the
current time.
Papers with different porosity that Existing banknotes vary in porosity
would be identified by blowing air during the course of their lifetime.
through them The possibility of controlling this
parameter within boundaries that were
even machine detectable was considered
unrealistic.
Piezoelectric effects Although natural fibers are known to
encompass piezoelectric
characteristics, it was considered that
the variations required when, for
example, bending the note, were beyond
current identification technology.
Olfactory detection The possibility of impregnating notes
with a microencapsulated odor was
considered impractical at present.
Problems of durability and cross odor
contamination eliminated this approach.
Shape (triangular, circular, etc.) The idea of having variously shaped
currency was considered impractical
from a manufacturing and handling
standpoint.
Patches applied after banknote The idea of adding features after
manufacture, indicating denomination by banknote manufacture was considered
location or texture impractical for two reasons. First a
large, localized area 100 µm or
more above the banknote "background"
would create problems (including
durability of banknotes, adherence of
the patch, and jamming of machines)
with automated cash-handling machines
and of uneven stacking. Second, there
is concern about the security
implications of having to match a
separate patch with a banknote after
printing processes are completed.
Thin silicon chip This technology is not considered
advanced enough for incorporation now.
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