I was printing this past Saturday with a colleague, Jim Hurtubise. I had came into a few boxes of old paper, and was running them through my usual test. I use a step wedge and make a grade 2 print, and then a grade 5 print. It lets me guage the contrast of the paper, as well as any base fogging. The paper was Forte Polygrade IV, which as you can see was fogged pretty badly. Almost a middle grey. I saw the results, and figured it was too far gone and chucked it in the garbage bin. Jim, not wanting to see any Forte go to waste, picked it out and said he'll try some lith with it. I made some cocky declaration along the lines of "if you want to waste your time with it, go nuts". Half an hour later he pulled this beautiful lith print out of the developer! I couldn't believe my eyes! Not only were the highlights a pretty clean white, but the dmax was significantly better as well. Never mind the beautiful image colour!
So: the print on the left, exposed at grade 5 and developed in dektol for 2 min 30 s. The print on the right is developed in homebrew D85 lith developer.
The moral of this story: no paper is too far gone to lith print with. Don't throw it out, give it to a lith printer and let them make something beautiful with it.