| abstract |
A timing device for visually indicating the passage of a duration of time is disclosed. The timing device and system, in accordance with the embodiments of the invention, is sectioned into zones with different rates of reactivity and/or sensitivity, such that the zones change color or darken over a range of times. The timing device, in accordance with further embodiments of the invention, comprises a film, that is a color film, a black and white film or a combination thereof, with a photographic layer and a developer layer, which when brought together activate the device. The photographic film can be pre-exposed to light or heat to control the rate that the film changes color or darkens after being activated. Pieces of timing film, in accordance with further embodiments of the invention, have adhesion layers for attaching the pieces of timing film to perishable articles or packages containing perishable articles and are preferably configured to be dispensed from a roll or stack of the timing film. |