Also, in the matter of gum over platinum and gum over cyanotype or vice
versa, there seem to be two issues: does it bleach out the first layer and
which looks better....
For some reason, dichromate seems not to bleach a cyanotype print (which
confuses me because I could swear I've seen it happen). But some tricolor
gum printers use a first layer of cyanotype for their blue printer
negative and then continue with the yellow and majenta printers over that.
In any event, if you do gum over cyanotype you can get the effect of two
colors by using a different negative or brushing off in areas. You don't
get the same duotone effect with cyanotype over gum, which raises the
question of why bother. Especially since it is so easy to get rich dark
hues with cyanotype and/or to tone the cyanotype brown or blue/black with
tannic acid.
Gum over platinum was the order used by the pictorialists and makes the
same kind of sense. While it's true that by putting down the gum first you
enhance the darks of your wishy-washy platinum, you also lose or at least
compromise the sensation of added color.
In both cases you have to go through the trouble of preshrink (tho I
suppose Terry would say that isn't necessary), and, seems to me, that's a
bunch of bother to then pull your punches (smother your color)
afterwards.....
Cheers,
Judy