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

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



Loris, I think this was discussed some time back in 95 or 96 amongst the
PT/PD printers. I forget who brought it up, possibly Bill Laven. I tried it
for some prints while living in Taos where RH can be extremely low 10% or
less. It did seem to offer some relief from poor coating. After moving to
Dallas and the much higher levels of humidity, I found that I gained very
little or no benefit from continued use. 

Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
http://e.neilsen.home.att.net
http://ericneilsenphotography.com
Skype ejprinter

> -----Original Message-----
> From: Sandy King [mailto:sanking@clemson.edu]
> Sent: Sunday, February 25, 2007 3:41 PM
> To: alt-photo-process-l@usask.ca
> Subject: Re: Glycerol as humectant for POP Pd prints at low RH
> 
> 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.