From: John Cremati (johnjohnc@core.com)
Date: 12/11/01-09:52:01 AM Z
Do you know the specific Ultra violet wave length that Dicromated colloids are most sensitive to..? I had read in a 1982 copy of VWR Scientific graphics supply catalog that all Nikon El Nikor Enlarging Lenses were made of a special optical glass to allow passing of UV waves between 350 and 450 nm.. I have also read of Sun enlargers utilizing sunlight as the light source thru a lens to enlarge during the turn of the century in the book "Keepers of Light "...
----- Original Message -----
From: <dsbryant@telocity.com>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Tuesday, December 11, 2001 9:04 AM
Subject: Re: Ultraviolet projection
> >
> > Folks:
> > Glass tends to absorb UV. Plate glass lets nothing through below 330 nm.
> > On the other hand, Quartz glass (no soda-lime or lead) is virtually
> > transparent to UV. I imagine that, in their french way, the Fressons are
> > noting that their enlarging lens and film holders are made of quartz glass.
> > I have used an OLEC 1500 watt unit to make direct gum prints. I placed
> > the unit above the enlarger housing with a small fan in between and had no
> > problem. Light output was reduced, however, to 1/2 its expected value
> > (measured with a UV meter) due to absorption by the system. Cheers, Ed
>
> So what kind of exposure times were you getting Ed?
>
> Thanks,
>
> Don Bryant
>
>
>
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