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

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 Wed Nov 23 01:40:39 2005