To get back to lumen printing, we tried again some over-age papers by exposing them to the sunlight. At the time of the tests the UV index was not yet very high in Finnish spring, but we exposed these prints out in the sun for several hours.
It seems that Dmax of these papers (used this way) is quite low, and you can not increase it by exposing more; with overexposure you just get your highlights murky and lower contrast overall. The print looks pretty nice right after the exposure, but will bleach considerably in subsequent wash and fixer (but I guess the fixer is necessary to ensure the printÂ´s longevity). Maybe we should try toning with gold or platinum, before the fixer, and see if it would prevent bleaching.
As it turns out, the paper prints the whole Stouffer 21-step wedge, all the way from step 1 to 21!