Re: Gum problem(s)

----- Original Message -----
From: <Ender100@aol.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, November 23, 2005 8:40 AM
Subject: Re: Gum problem(s)

> Just wondering if you could point me to the source for the spectra of
> sensitivity for different alt processes?
>
> Thanks,
> Mark Nelson

Being active in a somewhat different area (www.polygrama.com) mainly, I
don't quite feel qualified to answer your question. I assume Kosar would be
a good starting point. "Kosar" would imply not only his book but both the
literature he quotes from and the patents he refers to.
By the way I scanned the whole book to my computer (resulting in a slightly
messed up pagination). So I might be in the position to send out the whole
thing to those interested. That would be two multi-paged TIF files (5.8MB
and 4.6MB large)...

Martin

>
> In a message dated 11/22/05 9:30:39 AM, martinm@SoftHome.net writes:
>
>
> >
> > ----- Original Message -----
> > From: "Sandy King" <sanking@clemson.edu>
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Saturday, November 19, 2005 3:35 PM
> > Subject: Re: Gum problem(s)
> >
> >
> > > Dichromated colloid processes, including carbon and gum, have a
> > > maximum peak in the near UV at about 360 nm to 370 nm, varying
> > > slightly with pH and type of dichromate. From the peak at 360-370 nm,
> > > sensitivity falls off sharply to about 320 nm, at which point it
> > > starts to rise to another, and much large, peak at around 200 nm,
> > > where it has its maximum sensitivity. The peak at 200 nnm is really
> > > huge compared to the one at 360-70 nm, like Mt. Everest to the
> > > highest peaks in the Appalachians. On the other side sensitivity
> > > falls off very gradually in the violet and blue to near zero at
> > > around 520 nm.
> >
> > I don't think that's entirely accurate for dichromated colloid systems.
I
> > guess the data you quote, apply to the absorption spectra of a
dichromated
> > water solution.
> > When it comes to dichromated colloids, sensitivity peaks might be
> > considerably shifted towards longer wavelengths. By the way, speaking of
DCG
> > holography (dichromated gelatin), there are lots of people to expose
their
> > DCG layer at 532nm...
> >
> > Martin
> >
>
>
>
>
>
> Mark Nelson
> Precision Digital Negatives
>
Received on Thu Nov 24 06:47:19 2005