Estimation of print longevity
The test methodology assumes that images are stored in an archival album with a plastic cover sheet and kept in the dark. The 100-, 200- and 300-year figures assume an album in normal use.

Permanence is estimated by using an accelerated dark storage test (ISO 18924). Samples are printed with an initial optical density of 1.0 or 0.6 (for each of black, cyan, magenta, yellow) then kept in a controlled environment of high temperature and 50% relative humidity (RH) designed to accelerate colour fading. The rate of the decrease in the optical density and the rate of yellow discoloration of the paper are measured. Finally, the results are extrapolated to the length of time that a printed image can be kept at 23°C and 50% RH.

Estimation of light fastness
The 30-year light fastness figure assumes a typical indoor environment, avoiding direct sunlight.

Estimated light fastness is made under the following test conditions:
- Light source: white fluorescent light 70,000lux
- Temperature: 24°C
- Humidity: 60% RH
- A 2mm thick glass is placed on the sample during accelerated testing

The display life estimation (i.e. years before noticeable fading occurs) is calculated by dividing the total illuminance received before fading occurs by the assumed annual illuminance (assume daily illumination as 500lux x 10 hours per day and 365 days per year).

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