RE: DuPont Velour Black AND POP

DEAR MARTIN & RICHARD,
        Please note that developer type also influences how much fog will occur on
older papers. For example I have decade old Azo paper which appears fogged
when developed in Dektol but not in Formulary 130. I am guessing this has
to do with whether the developer works on the latent image sites on the
surface of the silver halide crystals or if it has a high concentration of
Sodium Sulfite, a complexing agent, which dissolves some of the crystals
allowing for development of internal latent image sites. The relative
concentration of KBr in the dev also influences the fog level.
        Sooooooooo try a few significantly different developers and, by all means,
try Martin's rehalogenating bath.
****Martin, I have some old Centennial POP which is showing significant fog.
I understand that it has extremely fine AgX crystals. I don't know if they
use a chloride or bromide salt to make it. Might a rehalogenating bath work
on it? Can you recommend a formula?
                CHEERS!
                        BOB

 Please check my website: http://www.bobkiss.com/

-----Original Message-----
From: MARTINM [mailto:martinm@SoftHome.net]
Sent: Monday, July 18, 2005 5:28 AM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: DuPont Velour Black

----- Original Message -----
From: "Richard Knoppow" <dickburk@ix.netcom.com>
To: "MARTINM" <martinm@SoftHome.net>
Sent: Sunday, July 17, 2005 11:31 AM
Subject: Re: DuPont Velour Black

> Anti-foggant in the developer can get rid of some fog but I think there is
a limit. > As I understand it some age fof is due to a continuation of the
ripening process. > Substances are added to the emulsion to prevent this but
are not completely >effective. I don't know if this is a reversable
process.

You might try this:
prior to exposure - insert the emulsion in a gentle rehalogenating bleach
for one minute, rinse and dry.
On ultrafine silver bromide emulsions EDTA proofed do nicely - without
destroying spectral sensitization.
Ferric EDTA..............20g
KBr...........................10g
water...........................1L

Some emulsions may require additional re-activation for one minute in a 1%
ascorbic acid solution, tuned to pH 6.

Martin

> ----- Original Message -----
> From: "Richard Knoppow" <dickburk@ix.netcom.com>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Saturday, July 16, 2005 7:41 PM
> Subject: Re: DuPont Velour Black
>
> > Velour Black has been discontinued for decades. Its
> > possible that some might still be around but probably too
> > badly fogged for use.
>
> It might be possible to kill the fog and re-activate the emulsion...
>
> Martin
>
>
> Well, I don't know how to do this. Anti-foggant in the developer can get
rid of some fog but I think there is a limit. As I understand it some age
fof is due to a continuation of the ripening process. Substances are added
to the emulsion to prevent this but are not completely effective. I don't
know if this is a reversable process. I don't remember when DuPont
discontinued Defender products but it must have been very long ago. Some
papers seem to have a very long shelf life. I've used some Agfa papers which
still worked OK after twenty years but some Kodak papers went bad in four or
five. I have no idea of how well Defender papers resist age fog. If I ever
see any old papers at a sale I may try them, if the price for them as
collector's items is not too high.
>
>
>
> --
> Richard Knoppow
> dickburk@ix.netcom.com
> Los Angeles, CA, USA
Received on Mon Jul 18 07:00:34 2005