Hi:

I have several questions regarding your problem:
1. Is this silver film or diazo?
2. What thickness polyester is being used? 4 mil (very common or 7 or 10 mil,
less common becuse of cost).  also, Mylar is a trade name - and photographic
film base is generically called polyester.

If it is silver film, one normally conditions the box of film prior to use in
the room in which it is being used. That room should have both humidity and
relatively tight temperature control to minimize growth.

Secondly, changing over to thicker polyester base will help but not totally
eliminate the problem.

Glass masters are extremely expensive and although they are better than film,
there are limitations. There are two dissimilar layers, one is glass and one
is a silver emulsion which is still sensitive to temperature and humidity
variations. Growth is more restricted but still occurs. It all depends on the
tolerances you are trying to keep.

Leo Roos

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