The other factor of age in my very cool/dry environment is that when air drying the papers curl to a point that makes flattening them in a mount press have a high risk of creasing on the edges, even when I warm them up with the press not clamped shut. I get best results from low temp drying on an old Premier drum dryer with a fresh new curtain.
But the paper has a soft emulsion that usually sticks to the muslin curtain, leaving some fibers and some texture behind. This only happens in my preferred neutral/alkaline fixer (TF-5 for prints). If I use Kodak Rapid Fixer with the hardener plus hypo-clear, it dries well in the dryer. That's a fine process, but I'd rather use the TF-5, skip the HCA and get cleaner washes faster.
There's the setup. Here are the long-winded questions:
I recently found the formula for Ilford IH-4 Formailn Hardener which is alkaline in pH.
Sounds like tough stuff. According to the Ilford Manual of Photography, 1958:Ilford IH-4 Formailn Hardener
Formaldehyde, 40% solution 10ml
Sodium carbonate (anhydrous) 5g
Water to make 1 liter
Immerse negatives or prints for 3 minutes. If used immediately after fixation and before washing, a short rinse should be employed after fixing. If used after washing, a short rinse should be given before drying.
I am thinking of mixing some up to use as an afterbath -- Fix TF-5, wash 20 min, IH-4, wash 10 min. I know nothing about how formaldehyde works in darkroom materials and how long the after-rinse should be for a fiber print. Ilford only said "short rinse." I figure washing the hypo out before the hardener would be most archivally effective. I had heard once -- possibly apocryphal -- that Photo-Flo contains formaldehyde and thus it probably has pretty good archival qualities since I used to soak negs in it decades ago that are still lovely.Formailn in neutral solution gives only a slight degree of hardening. The alkaline solution given above gives very considerable hardening, and negatives hardened in it will withstand boiling water. For this reason, films should not be immersed for more than the recommended time or they become brittle.
Thoughts chemists (Bill Troop in particular)?
Perhaps I might try formaldehyde in neutral solution first to see if I get enough hardening that way. Perhaps the alkaline solution might make the paper or emulsion more fragile.
This may be a thought experiment as it is no less trouble than pouring some KRF and HCA for this old paper. But it's fun to think about.