Re: A PVA for printing "gum" from Mike Ware

From: martinm <martinm@gawab.com>
Subject: Re: A PVA for printing "gum" from Mike Ware
Date: Sat, 01 Apr 2006 15:54:11 +0200

> In another paper (Lafond/Pizzocaro/Lessard/Bolte, Primary photochemical
> process in films of dichromated gelatin: a quantitative spproach, Opt. Eng.
> 39, March 2000) the authors showed Cr(V) to be quite stable both in
> dichromated gelatin and dichromated PVA. One of the most interesting aspects
> (at least for holographers) of Cr(V) consists in its strong absorption band
> around 520nm. That suggests it might be possible to "activate" a dichromated
> colloid (gelatin, PVA, possibly gum) with a weak overall UV exposure, which
> willl turn the Cr(VI) into Cr(V). Then the image exposure is carried out at
> a visible (non-UV) wavelength, preferably around 520nm.

What's your goal? If the goal is amplification, it may work to a
certain extent in converting Cr(V) to something else, probably
Cr(III), but 520nm irradiation ("flash exposure") cannot create any
additional imagewise Cr(V) so I think the degree of amplification is
very limited, and nowhere near the developer in silver-gelatin process.
Indeed, you may get all of the benefit of the flash exposure from
thermal reaction, rinsing or semiwet plates. Don't you think?
Received on Sat Apr 1 17:47:48 2006