For those not in the UK, it's worth mentioning that the last three months have not seen the amount of sunshine we would expect in a normal summer here and there have been a lot more overcast days than we would have liked. Therefore we would expect less fade from our window samples than more sunny countries would see.
At the end of three months exposure we have compared the three segments of each print to see how much fading has occurred. We've looked at the fading subjectively, comparing each segment with the segments that were protected from light fade by being in a drawer for the three months.
We've marked each print segment on a scale from one to ten and the scale works like this:
10 - no discernable fade.
8-9 - slight fade, but still usable.
7 - noticeable fade, borderline usability.
5-6 - considerable fade, print unlikely to be used.
1-4 - severe fade, unusable.
In addition to the fade tests, we performed a smear test on the prints at the end of their three-month fade test. We did it at the end of the fade test so there were no issues with inks not being properly dry. We drew a wet cotton bud down each print and checked to see if the bud was discoloured with ink. Those that produced no colouration on the cotton bud were scored as smear resistant. This is a simple yes or no result; we didn't attempt to assess levels of smear resistance