Re: Glycerol as humectant for POP Pd prints at low RH

[Sandy King <sanking@clemson.edu>]

Loris,

Congratulations on taking the time to test that premise. It is 
potentially a very useful piece of information.

Now, if more pt/pd printers  would take the time to learn carbon as 
you have no telling what kind of innovations we might see!!

Sandy King


At 11:18 PM +0200 2/25/07, Loris Medici wrote:
> 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.