My point is that you are using an acid (yes a weak one) on fragile, old and
possibly unknown chemicals on glass negatives. A person reading this list
might even be tempted to soak the item for some time in what they thought
was 'pure' and therefore unreactive water. I thought it was appropriate to
point out that distilled water can in fact be reactive.
I'm not claiming to be an expert on what materials might have been used on
glass neg's, and whether there was any chance of a reaction with weak
carbonic acid. It is possibly not an issue at all. But I think the person
who owned those negatives might be a little miffed if they discovered
otherwise, and telling them that acid rain would have caused 10-100 times
more damage would be little consolation!
Perhaps there is someone on the list who is, or knows, an expert on old
emulsions?
MT
>A pH of 5.0-5.5 is very weakly acidic: neutral is 7.0 and pH is a
>logarithmic ratio. Acid rain for example has a pH of less than 4 (10 to 100
>times more acidic than what you're talking about). Is 5.5 really dangerous
>to film?
>
>Frank Paris
>marshalt@spiritone.com
>
