Re: A little gum test

Eeeeeeeek! In my opinion, it doesn't matter if it works!!!!! BTW, here in
tiny little N.Z. we don't use high-tech windows much-certainly not in our
under-funded Tertiary institutions ;)
Kate
----- Original Message -----
From: "MARTINM" <martinm@SoftHome.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, December 16, 2003 10:11 PM
Subject: Re: A little gum test

> "Ordinary crown window glass transmits a very high percentage of UV
> radiation over 350nm, and some UV even as far down as 300nm."
>
> You are certainly right for plain thin crown glass plates. What about
modern
> windows that might imply highly isolated double or triple glasses, UV
> coatings, special gas filling etc.?
> And what about secundary effects of "indirect illumination"? How much UV
> gets absorbed or transformed into visible radiation by means of white
> painted (titandioxide white) walls?
>
> Martin
>
> ----- Original Message -----
> From: "Sandy King" <sanking@clemson.edu>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Tuesday, December 16, 2003 6:37 AM
> Subject: Re: A little gum test
>
>
> >
> >
> >
> > >
> > >If your windows are closed, there will be practically no UV light at
all.
> > >This might suggest you actually expose your gum layers at - visible -
> > >blue/violet radiation (which in fact would not be too surprising given
> > >dichromated
> > >colloids are sensitive from UV - ~550 nm)...
> >
> >
> >
> > 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.
> >
> > 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 14:14:04 2003