Longevity of lifted footprints - Lifted shoe prints (dust marks) may slowly fade in time. For very weak prints this may be noticeable after storing for a few days. This will depend on temperature. The lower the temperature, the slower the fading. This, however, should not be a concern since lifted footprints can easily be photographed after removing the cover sheet. Oblique lighting will show details not visible before photography. So far, no materials are known to us that faded on the lifter surface before satisfactory photographs had been taken.