Appendix E:
Features Not Subject to Full Evaluation
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.
Table E-1
Features Not Subjected to a Full Evaluation
Feature |
Rationale |
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. |
Feature |
Rationale |
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 currency, with number of windows indicating denomination |
This feature would not be suitable for blind people. It would also require largesized 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 on end side with rough center |
From evidence of tactile perception, 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. |
Feature |
Rationale |
Papers with different porosity that would be identified by blowing air through them |
Existing banknotes vary in porosity during the course of their lifetime. The possibility of controlling this parameter within boundaries that were even machine detectable was considered unrealistic. |
Piezoelectric effects |
Although natural fibers are know 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 manufacture, indicating denomination by location or texture |
The idea of adding features after banknote manufacture was considered 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. |