Recipe for Interactive Art

One US Dollar Banknote

  1. The machine should be a parallelepiped with the following dimensions (within a 5 cm allowance):
    • Height = 1.4 m
    • Width = 1 m
    • Depth = 1 m
  2.  The bottom part of the machine should be a short (about 10 cm high) socket finished with brushed steel;
  3. The middle part of the machine should be an empty transparent tank of 1 m³ internal capacity. This capacity should be as exact as manufacturing technology allows (see notes);
  4. The upper part of the machine should be a brushed steel covered parallelepiped, following those specifications:
    1. One of the sides of the machine should bear a large digital display, containing a decimal currency value;
    2. That same side should bear a banknote slot;
    3. The other sides of the machine should be kept as simple as possible, eventually containing (if absolutely necessary) ventilation slots, holes for the cables, service accesses etc., but in no hypothesis decorative elements;
    4. The cabling should be as discreet as possible;
    5. Internally, the machine should contain a recto-verso image scanner, a computer, a secondary-memory storage device and a paper shredder;
  5. The machine should operate as follows:
    1. A banknote is inserted in the slot;
    2. The banknote is scanned on both faces;
    3. The machine identifies which currency and value corresponds to the banknote;
    4. If the banknote cannot be identified, it is returned;
    5. If the banknote can be identified, the following events should occur:
      1. The banknote will be shredded into tiny bits (no larger than 5 ×5 mm), which will be thrown on the tank below;
      2. The value of the banknote will be converted to the reference currency;
      3. This converted value will be added to the value on the digital display in front of the machine;
      4. The image of both faces of the banknote will be stored in the memory device with these metadata: a sequential id, a timestamp, the identified currency, the identified value, the value in the reference currency;
  6. While on display, the machine should be left operating, with the public allowed to insert banknotes on it. If the machine needs to be stopped for more than a short while (e.g., to be serviced), it should be removed from display (either physically, either by being covered with an opaque crate);
  7. When the tank becomes full, its contents should be compacted and left at the bottom, and the machine should resume operation;
  8. When the tank becomes unredeemably full, the machine should be retired, with the following provisions:
    1. The tank should be removed and sealed with a transparent cover;
    2. The tank should be put over a cylindrical socket (H = 20 cm, Ø = 110 cm, white matt finishing);
    3. The storage device should be removed from the machine;
    4. The storage device should be put over a cylindrical white socket (H = 120 cm, Ø = 25 cm, white matt finishing);
    5. The tank and the storage device should be displayed together, near each other, but as independent pieces, with the labels “9999 $ in 1 m³” and “9999 $ in XX GiB”, substituting 9999 by the appropriate value, $ by the appropriate currency and XX by the size of the data stored in the storage device;
    6. The remaining parts of the machine should be destroyed and discarded.


  1. The tank dimensions may vary considerably as temperature changes. The tank should therefore be dimensioned accordingly to the expected exhibition conditions. Consider also that, once full, the integrity of the tank might be jeopardized if it shrinks as temperature drops. A tough material which changes little with temperature might be the best choice for the tank, on the other hand ordinary Plexiglas might be particularly ill-adapted;
  2. The memory storage technology should be chosen to be very compact, error-tolerant and to keep the bits reliably for a long time. Currently, the best compromise would be either a small form-factor hard-disk drive, either a solid-state drive ;
  3. The reference currency should be the currency of the place where the machine is located. If the machine is expected to travel across places with multiple currencies, U.S. Dollars should be used instead;
  4. For reference, if the machine is fed only usual USD banknotes, about 883 thousand notes will be necessary to fill the tank, the total weight of which will be 883 kg;
  5. For reference, if all those notes are 100 USD bills (highly unlikely), the display will need 12 decimal digits (8 units before the decimal point and 4 after);
  6. For reference, if no data compression is used and those notes are digitized at 600 dpi (236 dpcm), each will need approximately 11 MiB for a recto-verso scan, resulting in 9.3 TiB of data; for 100 dpi (40 dpcm) resolution, this is reduced to about 260 GiB of data — a compromise between resolution, compression and available technology for the storage device may be sought;
  7. The memory device should be designed so to be extremely unlikely that it will fill before the tank. And if this ever happens, the machine should be temporarily removed from display, the data should be transferred to a new, roomier device, and the original device should be destroyed;
  8. Intently destroying currency is illegal in most jurisdictions. It is possible (but by no means guaranteed) than an exemptions could be obtained if the curator agrees to refund the Treasury the cost of replacing the destroyed banknotes.

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