RE: Glycerol as humectant for POP Pd prints at low RH
DEAR LORIS, I am just wondering if the polyvinyl alcohol that I add to my DOP PT/PD coatings serves a similar purpose? Of is it just to make coating easier? CHEERS! BOB -----Original Message----- From: Loris Medici [mailto:mail@loris.medici.name] Sent: Sunday, February 25, 2007 5:18 PM To: alt-photo-process-l@usask.ca Subject: 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.
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