Re: Water and gum coating

"Is there a reason why erythrosin is preferred for that wavelength over
cyanin or merocyanin dyes of similar absorption spectra?"

I understand the main reason is the dyes need to be photoreduced in the
presence of an electron donor. I ignore if this can be done with cyanines.
Probably not easily since that kind of photopolymer systems is usually based
on
thiazine and fluorescein dyes.
In a simple experiment you can bleach a mixture of gum (or an other colloid)
+
triethanolamine + methylene blue under red light (to some extent even
holograms can be recorded on such layers).

"But your formula is not adding PVA to the acrylamide stock but adding
to the dye stock instead. Why?"

Actually PVA can be mixed into that solution.

"Can you really get enlarging speed with it?"

I suppose so - given such layers are exposed with a few Milliwatts of laser
power.

Martin

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>; <martinm@SoftHome.net>
Sent: Thursday, May 20, 2004 10:44 AM
Subject: Re: Water and gum coating

> From: MARTINM <martinm@SoftHome.net>
> Subject: Re: Water and gum coating
> Date: Thu, 20 May 2004 09:18:48 +0200
>
> > I guess a great many photopolymer system exist that may work in that
sense.
> > E.g. acrylamide systems achieve speed levels somewhere between silver
> > halides and dichromates. In addition they can be spectrally sensitized:
> > erythrosin, rose bengal etc. for green and methylene blue for red
exposures.
>
> Is there a reason why erythrosin is preferred for that wavelength over
> cyanin or merocyanin dyes of similar absorption spectra? Well,
> erythorosin is very cheap anyway, one good thing if it works.
> (So is methylene blue.)
>
> > Adding PVA to the solution will provide sufficient protection from
oxygen
> > (which inhibites radical polymerization).
>
> But your formula is not adding PVA to the acrylamide stock but adding
> to the dye stock instead. Why?
>
> Can you really get enlarging speed with it?
> --
> Ryuji Suzuki
> "You have to realize that junk is not the problem in and of itself.
> Junk is the symptom, not the problem."
> (Bob Dylan 1971; source: No Direction Home by Robert Shelton)
Received on Thu May 20 21:35:36 2004