From: Katharine Thayer (kthayer@pacifier.com)
Date: 11/09/01-11:15:28 AM Z
Judy Seigel wrote:
>
> I don't remember Zimmerman's dates, but the method of putting the
> potassium dichromate in the bottle with as much water as possible then
> topping off with more water as it ran low was in common use early in the
> century and often advised in how-to articles.
>
Well, sure, that's fairly well-known. It was the amount that amused me,
the idea of putting a whole pound, enough to make 3 1/2 liters of
saturated K dichromate, if my arithmetic is right, into a pint bottle.
It seemed like overkill to me, although I understand the logic of
ensuring you always have a saturated solution by keeping excess
undissolved material in the bottle. The logic kind of falls apart toward
the end, though, because you would have to either put a new pound in
some time before the old one was gone, or keep the water level lower and
lower to make sure you're keeping a saturated solution as the dichromate
becomes used up. It seems like a lot more trouble to me than just mixing
up a couple hundred ml of solution every now and then.
> About the Zimmerman process itself, there were comments in subsequent
> articles of the period, most of them (as I recall) finding the faults, or
> saying it failed. The fact that it seemed to get little if any following
> is probably also a comment.
Thanks, that confirms my general impression. And you're right; with
digital negatives, who needs projection speed gum anyway? Good point.
kt
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