Re: red safe light

I think the key is to have a tungsten light bulb which gives out very little
if any UV. The color does not matter, some clear (or almost clear) material
will block UV. Think of flash tubes for example.

In some cases another cause of fog is heat and not much of it for that
matter, room temperature is plenty enough for some activity to happen either
physical or chemical.

Yves

----- Original Message -----
From: "Sandy King" <sanking@CLEMSON.EDU>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, November 10, 2005 9:12 AM
Subject: RE: red safe light

> Yes, that was my impression also. I did some work with salted paper a
> few years ago and worked in a room with a 100 watt yellow bug ligh,t
> as I do with other alternative processes, and did not get any fogging
> from the light.
>
> Sandy
>
>
>
>
> >DEAR LIST,
> > All along I thought that salt prints were only sensitive to UV so ANY
> >source that had the UV filtered out was fine. I believe that is what
Ryuji
> >is saying...yes? Am I wrong here? So why the red safe lights?
> > CHEERS!
> > BOB
> >
> > Please check my website: http://www.bobkiss.com/
> >
> >-----Original Message-----
> >From: Yves Gauvreau [mailto:gauvreau-yves@sympatico.ca]
> >Sent: Thursday, November 10, 2005 5:29 AM
> >To: alt-photo-process-l@sask.usask.ca
> >Subject: Re: red safe light
> >
> >Ryuji,
> >
> >assuming we are talking of a UV safe light, any color above the UV range
> >would theorically work. In reality, most of the materials used to filter
out
> >the UV or any other range of the spectrum, are far from perfect and
> >especially they don't usually have a sharp cutoff in desired range. You
can
> >visualise this a bit like a graduated filter and the darkest area would
be
> >placed in such a way as to block the UV range (partially) and letting
most
> >of the other colors or frequencies go through barely affected. A good UV
> >filter would need an effect something like a 8 EV or stops maybe more in
the
> >UV range to work. It all depends on the sensitivity of the material your
> >using.
> >
> >The physics of light would suggest that a red translucent material like
the
> >one used on the Home Depot bulb would probably have an effect on the UV
> >range but maybe it wont be enough. As I said above, the dimming effect of
> >this specific red material on the UV range isn't known, for example an
> >infrared sensitive film (IR) also have a similar sensitivity in the blue
> >range.
> >
> >A red filter like the Wratten #25 as only about a 10 stop blocking effect
on
> >the UV while a #8 (yellow K2) is blocking even more UV then that.. As you
> >can see, it's more a question of the response of a material then only
it's
> >color.
> >
> >Yves
> >
> >
> >
> >
> >
> >
> >----- Original Message -----
> >From: "Ryuji Suzuki" <rs@silvergrain.org>
> >To: <alt-photo-process-l@sask.usask.ca>
> >Sent: Thursday, November 10, 2005 2:50 AM
> >Subject: Re: red safe light
> >
> >
> >> From: Judy Seigel <jseigel@panix.com>
> >> Subject: red safe light
> >> Date: Thu, 10 Nov 2005 02:38:21 -0500 (EST)
> >>
> >> > (I've also had fogging when my red photo bulb got scratches -- most
of
> >> > them are made with a red lacquer sprayed on top of a regular plain
> >bulb...
> >> > which can scratch, flake or crack. I patched with red nail polish.)
> >>
> >> Does it have to be red? What difference does it make?
> >>
Received on Thu Nov 10 11:47:29 2005