Interview with Henry Wilhelm on print permanence

Critical to be able to map accelerated test data for image permanence
on to real world projections is to know what the real world is like.
And the only way to do that is to go out and make systematic
measurements in the environment for which you are trying to make
predictions. (An office, for example, is quite different from a home
which is quite different from a museum.)

That takes time, money, and discipline, and to my knowledge only one
organization has done this world-wide and published the results in a
refereed journal where other photoscientists could critical examine
the data before and after publication (it's not Wilhelm Imaging
Research).

Look up the papers by Dr. Douglas Bugner and colleagues (and before
that by Anderson and co-workers), all in the Journal of Imaging
Science . They measured light, temperature, humidity, and ozone in
homes around the world. They did continuous measurements, not spot
readings which can vary by more than a factor of ten over the course
of a day. They measured it in different seasons. And they measured the
power spectrum of the light in the homes, which is critical to using
the right light in testing (you can even get the wrong rank order of
dye fade--one product to another--if you use the wrong light
spectrum).

And then they did what one poster suggested: they hung real prints in
real homes and checked over a ten year period--not to see how those
particular materials faded, but to calibrate their test methods.

Further, work by those authors, as well as yet to be published work by
Adam Bush has shown that balancing those four factors in the right
proportion is absolutely necessary to even predict that one print
product will last longer than another in the real world. To put it
bluntly, you will get the wrong answer--not just in years but in
relative ranking if you don't use typical real world values.

(By the way, look at the data offered by some testing sites on the
web: strange how some products tests for, say, ozone are still "in
progress" several years after the light tests are published, even
though ozone tests are the fastest to do. Remember, manufacturers pay
for those tests.)

Bottom line: tests run under the wrong conditions--the infamous
"window test" is a good example--won't tell you which print material
will have the best image permanence in a real world environment--
unless your real world enviroment is mounting in a window.