From: T. E. Andersen (postlister@microscopica.com)
Date: 06/09/03-09:43:42 PM Z
Hi!
I've used mylar too (for cyano, vanDyke and polymer plates), even much
thicker than .0005 (I believe I used 125µm). As most of the alternative
processes have sensitivity peaks between 350nm and 400nm, the loss of
UVB should not represent a problem! Actually, mylar is used all the time
in the graphical industries, and meny of the plates they are using have
very similar spectral sensitivity to common alternative processes. UVB
is likely to be blocked from your ligh source to begin with, as it is
not very healthy to expose yourself to it. The atmosphere filters out a
lot of the UVB, so this goes for the sun as well...
Best whishes,
T.E. Andersen
Sil Horwitz wrote:
> At 2003-06-09 06:50 PM +0000, you wrote:
>
>> I have used .0005 mylar for two purposes in gum printing: (1) as a
>> protective barrier between the negative and the paper, to protect the
>> print when I've used a freshly-oiled paper negative that hasn't been
>> given enough time to dry properly, just to be absolutely sure I don't
>> get any oil on the emulsion, and (2) as a base for cliche-verre
>> negatives. It's been a while since I've done either; I don't remember
>> the mylar barrier slowing down the printing of the paper negative enough
>> to notice, but I do remember clearly that the mylar cliche-verre
>> negatives printed in significantly less time than oiled paper or
>> Pictorico negatives (1 minute or less vs. 3-5 minutes). So I'm perplexed
>> at the news that mylar blocks UV light.
>
>
> From the specs for Mylar (polyester) film:
> / Mylar – blocks UVB only, transmits UVA and visible.
>
> /Under UVB light (I don't know the specific wavelengths involved) Mylar
> looks black as it does not transmit those light frequencies. Since we
> need all the UV we can get, my opinion is that Mylar is not suitable for
> work requiring UV exposure. As an example, Mylar film is used for
> archival storage because of its resistance to atmospheric pollutants and
> its UV blocking characteristics.
>
> ---sil
> Sil Horwitz, FPSA
> silh@earthlink.net
> personal page: http://www.silphoto.us <http://www.silphoto.us/>
>
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