Tom Sobota (TSOBOTA@teleline.es)
Thu, 14 Jan 1999 10:32:54 +0100
Henk,
Some fourteen years ago, when I came to Madrid, I prepared about 3 liters
of gum, as well as a saturated solution of K Dichromate. These have been
thru the rather uncomfortable yearly temperature cycles of Madrid, from
near zero Centigrades in winter to nearly 40 C. in summer since then,
without apparent ill effect.
The gum solution is kept in a brown glass bottle, and the dichromate in a
plastic bottle that once contained Rodinal, I think. Yes, I washed it
before...
I have since prepared new gum and dichromate solutions, but I still use the
original ones from time to time and they work fine. I work mostly by eye,
so there could be differences, but in any case these are not _too_ noticeable.
I don't use formaldehyde as a conservant, but rather a few crystals of Thymol.
Your problem looks like it might arise from too much formaldehyde, having
insolubilized the gum.
There could be some difference between keeping properties of K Dichromate
and Am. Dichromate, granted, but if the sensitizer went bad for some
reason, you'd have a coat of soluble gum on your paper, dissolving away in
the first minutes of development.
Bye
Tom Sobota
tsobota@teleline.es
Madrid, Spain
At 09.25 13/1/99 +0000, Henk wrote:
(...)
>Question is : how long can a solution be trusted to be ok under normal
>conditions -room temperature, brown bottle etc.
>What about the Am.Dichromate in that sense, any chance that solutions in
brown
>bottles will change if not kept in the dark?
>Thanks in advance,
>
>Henk
>
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