U of S | Mailing List Archive | alt-photo-process-l | Glycerol as humectant for POP Pd prints at low RH

Glycerol as humectant for POP Pd prints at low RH



Hi all,

Probably I'm not the only smart person to tried this before but since I haven't found a reference in the list archives, I decided to share:

I was having hard time making cold/neutral toned POP Pd prints lately; the RH of my darkroom changes around 25-30% and printing w/o drying thoroughly (in other words: with almost wet paper) isn't a good choice since I'm using a relatively weak digital negative substrate and printing on almost-wet paper = ruining the negative due excess humidity. (The negative substrate I use is Ultrafine Crystal Clear.) I also don't prefer to use a thin (1-3 mils) polyester sheet between the negative and the paper because sharpness will suffer... (I'm printing using a 11x14" contact printing frame and a bank of BL tubes.)

Anyway, given the above criteria, I decided to put glycerol (glycerine) into my coating solution. Since this compound is used as a humectant in both carbon printing (tissue will retain humidity when some glycerol is present and won't brittle) and silver-gelatine emulsion making, I thought it may help me in retain humidity in the paper -> letting me get cold/neutral tones.

It works! I added a drop of glycerol per 10 drops of coating solution, dried the paper for 10 minutes and got a neutral print. Without the glycerol - keeping all other parameters constant - I would get a warm (brown) print.

Do you think adding glycerol will affect longevity? I'm using very little... (0.1ml per 1ml coating solution)

Regards,
Loris.