<< Fairly often by the way, I simply dilute the dichromate when mixing up the
emulsion. I normally use a 26% ammonium dichromate solution, and, let's
say, I want a mix to keep for a while, or the weather is hot and muggy,
which always speeds things up, so I cut it by half with water... or
whatever. I don't think it cuts the speed so VERY much (maybe the excess
particles kick in, like Mike said.)
>>
Judy, this is very interesting. My record (it's a just-so-happened record, not
a formal test) shows that I lost speed going from saturated potassium
dichromate to 10% solution! Maybe with ammonium dichromate, 26% solution has
much much more than enough dichromate and when you dilute to about half it
still has more than enough dichromate that one doesn't see any difference?
However, I have to admit that I didn't keep good record on this one. I do have
a bottle of *old* 10% solution, and you did mention that the solution lost
speed with age. Now I forgot whether I was comparing the saturated solution to
a new 10% solution or to the old 10%. I believe I did both and can't be sure
now. :(
But I didn't do another test because at this point speed is not a critical
issue for me as long as the exposure is reasonably consistent. For me, the
"bottle neck" of the system is in the development, so exposure time difference
is not really that important.
But I like the recent, serious discussion about gum. :)
Dave