From: Judy Seigel (jseigel@panix.com)
Date: 11/09/01-03:22:53 PM Z
Forgive me if this came through already, but if it did, I missed it... and
am still wondering:
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Keepers of Light has a formula for "Red-Brown tones" in cyanotype achieved
by toning for 5 minutes in a solution of tannic acid, followed by a
solution of sodium carbonate. It says however that "in about a week the
highlights will begin to turn yellow."
I've never seen any yellowing in tannic acid-toned cyano, but then the KOL
formula is about 15 times as strong as the one I use. (Mine is 2 grams of
tannic acid per 1000ml water, his is 6 grams per 180 ml water... so I
guess that's MORE than 15 times.)
As I recall, we discussed this on the list some years ago... at which time
nobody else seemed to have seen that yellowing either. However, I have
now come across the statement again elsewhere, and wondered if it could
be true after all -- or if it was simply copied from KOL, as is my guess
(& so often the case with these things).
I CAN'T test it myself, because I can't find my tannic acid (really,
there's a lot of STUFF, especially in JARS around here) -- and tannic acid
being as light as it is, 6 grams would be a heap. Meanwhile, noticing some
cyanotype toning persons in the crowd of late, thought I'd ask again....
Any ideas? Anyone know where the KOL original might have come from?
I've never seen it anywhere else. (Though it also occurs to me now that
that concentration of tannic could turn anything tea yellow...)
TIA, cheers, etc....
Judy
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