From: Sarah Van Keuren (svk@steuber.com)
Date: 04/29/00-08:46:13 PM Z
> I used some Tannic acid once and it stained the paper.
> It was kind of old, would that matter? Maybe my
> dillution was wrong. Does anyone have a formula for
> the Cyan toning?
> Jonathan Long
A simple toning process that I have used and taught for years consists of
bleaching a cyanotype in dilute household bleach (NaOCl) and bringing back
whatever got bleached away in tannic acid. With a continuous tone negative
partial bleaching can give a duotone result: purplish-brown highlights and
blue shadows. A high contrast or halftone negative would bleach away
entirely and come back in brownish tones only.
I don't measure the bleach or the tannic acid since both are done by eye but
the bleach could be 1:32 with water and perhaps 1/3 of a cup of tannic acid
can be sprinkled over the top of water in another tray. The tannic acid
continues to darken the print as it washes and dries ‹ a bit the way it
happens with vandyke. A warmer rosier brown can be gotten by returning to
the bleach briefly after immersion in the tannic tray. Don't try to print in
gum on top of a cyanotype toned this way unless you like dirty orange
highlights. The tannic acid bath does tint non-image areas of the paper
somewhat but not as much as tea does.
Tannic acid powder, that smells like tea but shouldn't be inhaled, can be
obtained from Rembrandt Graphics Arts, a printmakers' supplier in Rosemont,
NJ, phone 800 622-1887, email: sales@rembrandtgraphicarts.com. One pound of
the powder costs $12.75, 1/4 lb. is $4.55. I doubt that it matters if the
powder is old but once it is dissolved in water it is good for only one
session because stuff begins to grow in it though I can't say what it is
that would thrive in such a liquid.
Sarah Van Keuren
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