From: Sil Horwitz (silh@earthlink.net)
Date: 06/09/03-09:01:32 PM Z
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
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