Re: A little gum test

On Tue, 16 Dec 2003, Sandy King wrote:
>
> I question your statement that if the windows are closed there will
> be practically no UV light at all. Ordinary crown window glass
> transmits a very high percentage of UV radiation over 350nm, and some
> UV even as far down as 300nm.

What I thought of is that our UV light bulbs are made of glass --
sunlamps, fluorescents, the lot of em... I know the BLB bulbs have special
glass to keep the visible light from getting out -- but how special are
the others?

Judy

>
> It is true that colloids have some sensitivity up to 550nm, and
> radiation at this wavelength could expose a gum print. But it would
> take a very, very long time. My opinion is that in the situation Kate
> describes a lot of the radiation is indeed in the UV range below
> 400nm, especially considering the relatively short exposures she
> describes.
>
> Sandy King
>
>
>
>
>
>
> >
> >Martin
> >
> >----- Original Message -----
> >From: "Kate Mahoney" <kateb@paradise.net.nz>
> >To: <alt-photo-process-l@sask.usask.ca>
> >Sent: Monday, December 15, 2003 8:49 PM
> >Subject: Re: A little gum test
> >
> >
> >> What's really interesting is that I NEVER use direct sun - all my prints
> >are
> >> exposed in a corridor with high windows which reflects a lot of light -
> >but
> >> I think the UV must be high because digital shots in the area always come
> >> out very blue on daylight setting. You would hardly think that 4 min
> >> exposures in diffuse light would be overexposed!
> >>
> >> Kate
> >>
> >> ----- Original Message -----
> >> From: "Katharine Thayer" <kthayer@pacifier.com>
> >> To: <alt-photo-process-l@sask.usask.ca>
> >> Sent: Monday, December 15, 2003 1:09 PM
> >> Subject: Re: A little gum test
> >>
> >>
> >> > Kate Mahoney wrote:
> >> > >
> >> > > Hi Mark, Less contrast with the saturated solution was
> >> > > postulated....so I'thought I'd give it a whirl. I have been getting
> >> > > rather flat prints so this is good news. The results (to me) show some
> >> > > of the reason why I've been having some trouble with this technique -
> >> > > obviously too much amm.di. I think the reason why the tones are better
> >> > > is that mostly I've just been overexposing with the amm. di. at the
> >> > > more concentrated level...
> >> >
> >> >
> >> > Thanks Kate, this provides some confirmation for a suspicion I've had
> >> > for some time, that when people say that saturated ammonium dichromate
> >> > prints flat, perhaps what they really mean is that they overexpose when
> >> > they print with saturated ammonium dichromate. I have never observed
> >> > that saturated ammonium dichromate prints flat when properly exposed.
> >> > That not only the shadows but the highlights were blocked (I'm assuming
> >> > you mean after a reasonable development time) suggests that the problem
> >> > was related to significant overexposure, as you suggest above, rather
> >> > than to the contrast range of the saturated dichromate per se.
> >> > kt
> >> >
> >>
> >>
> >>
>
Received on Tue Dec 16 09:49:25 2003