Re: Extending The Spectral Sensitvity of Gum Bichromate

Alex Nanson (alec@norlex.demon.co.uk)
Tue, 10 Dec 1996 22:52:25 +0000

In message <961210003856_101522.2625_IHW61-1@CompuServe.COM>, Terry King
<101522.2625@CompuServe.COM> writes
>Alex
>
>I wondered in what circumstances extending the spectral sensitivity would offer
>anadvantage ?

Terry,

I use a small Diazo photoprint machine (a Bruning 70 ),for carrying out
quick trials on gum bichromate formulations. The machine is compact
(desktop), the lamp section is totally enlosed and fan cooled, but the
machine is somewhat limited with regard to multiple printing. The
machine is also very useful for printing Cyanotypes, however.

When I get something interesting I contact print it using the big UV
source in the sky. However, this appears even more infrequently over
Gloucester than it does over Twickenham. (I originate from Isleworth, so
I speak from experience).

I also use some small sunray lamps, these are quite slow, and put out a
lot of heat. I wondered therefore, that if it were possible to shift the
sensivity towards the red, I could use daylight even on relatively dull
days.

Thus I would also save myself the time and expense of building a UV
source from scratch.

I've ordered one or two chemicals from Mr Aldrich, and I hope to carry
out some tests in the new year. If I get any results I'll post my
findings

Although I suspect that like most of my ideas , it is just wishful
thinking!!

Alex.

Alex Nanson
Gloucester UK