Each emulsion ages differently on paper. It depends also on the conditions
of drying and storage as well as the paper itself. That is to say, some
papers will store relatively well (especially in cool dry weather) with
some of the better-storing emulsions (say, cyanotype & VDB) but other
papers, perhaps with different pH don't.
Also, generally speaking, what happens is that the paper fogs over time --
the top tone might be higher, but the emulsion hasn't necessarily gotten
faster -- that is, the bottom tones can have gotten higher too, so the
actual *range* remains the same. Also, odds are the whole business is
flatter, so you've lost contrast.
In other words, each combination is sui generis -- you have to test. But
applying the emulsion for almost all processes is fairly quick and easy.
And since the mixes do keep *in the container* 73667.2064@CompuServe.COM (changes there are much
slower), that won't be your biggest problem.
Good luck,
Judy
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