My so-called "server", with a mind, so to speak, of its own, put this
report (written two days ago) on "postpone" where I happened to spy it
while looking for something else. I think it's interesting enough to
send now, even as old news:
Mike Ware's instructions for what to do with bad am fe cit were "1 drop 20%
dichromate to every 10 ccs sensitizer."
Being a thrifty housewife type I was doing the UV-bulb tests with only 20
*drops* each of A&B. So I took one drop of 26% am dichromate, which is
what I had, & added 10 drops distilled, then added one drop of that mix to
20 drops part A (am fe cit) then added 20 drops part B (k fe) to get a
cyanotype emulsion with more or less the amount of am di Mike called for.
The B went into the A with no blue precipitate -- all hail Dr. M.
But that was so easy I decided to push the envelope, use a lower
proportion of am di. Mike had said it would increase contrast, & I preferred
to change contrast less. So I added one drop of the approx 2% am di to
*25* drops of part A. Just the first drop of part B brought instant dark
blue precipitate.
Next I thought maybe I could add a tad more A & B to the already-mixed, OK
sensitizer. That is, I added 1 drop of the diluted am di to 20 drops A,
added the 20 drops B, and mixed (getting nice clear emulsion as before),
then started to add a bit more part A. At the very first drop, dark blue
precipitate.
Which leads me to believe that Mike Ware has either done some heavy math,
or rules molecules both sides of the Atlantic. (And OK Mike, since you
know so much, can I get the dichromate stain out of my negative with a
drop of this & that? When my students blob up their negatives with wet
emulsion I lecture them on carefulness & say it's a total loss. But now
it's happened to me! And right in the middle. Of *two* negatives! I'm
thinking of a bleach & redevelop bichromate "stain remover." Anybody?!)
Well I digress, and all this did take less time than the telling, so there
was still time for the original mission: to compare 21-steps printed in
cyanotype by Cool White, Black Light, and my 3 brand new Daylight
fluorescent bulbs (which cost $6.50 each at Garbers; and let me note once
more -- BL being $12 on Canal St, the Daylight is not a humongous
saving given all the givens).
Mike said the added dichromate would increase contrast... not having good
"regular" emulsion to compare (when snow clears I'll get some GOOD am fe
cit) I have to reserve judgement on that.
What I can say for sure is that the midtones were distinctly grainier than
usual, tho persons who print cyanotype on (ugh!) a rough paper like Rives
BFK would not notice grain the size of chic peas...
However, that itty bitty drop of added dichromate slowed speed
dramatically. It took 12 minutes exposure by the blacklight bulbs to get
my standard 3- minute exposure. But being by now tired of this game, I
didn't test the other bulbs for 12 minutes. Here are the results with the
dichromated emulsion of all three bulbs for my usual normal-for-cyanotype
3-minute exposure:
If you put cyanotype on a scale from one to a thousand, one being the
least visible blue, a thousand being the best possible full rich print,
the cold white bulbs were 1
the daylight bulbs were 3
the blacklight bulbs were about halfway to a good print, in the 467 to 523
range....
More to follow on Daylight bulbs with gum.
Judy