Re: old cyanotype formulae

[Judy Seigel <jseigel@panix.com>]

On Mon, 20 May 2002 CCBaggett@aol.com wrote:

> Photographic Facts and Formulas  E.J. Wall dated 1924

CUT

 "Brighter prints are obtained by the addition of 0.5% of
> Oxalic Acid to the above; the paper keeps better if 0.05%  of Potassium
> Bichromate is added."

Potassium bichromate as preservative for cyanotype emulsion may be true on
the planet Mars... but my finding was that it actually made a terrible
print under most circumstances... The variables included size added to the
paper, and which size (gelatin or starch), also how long the emulsion was
on the paper, and how long the size had been on the paper, among others..
(I showed some of them in the "cyanotype issue" of P-F, #5, page
31).

In fact I found cyanotype poster child for old formulas not printing as
stated.... My guess is that none of the workers then had the Internet and
didn't realize how many variables there really were. If something "came
out" for them in one set of conditions, they assumed it was a universal.

The old books are riddled with stuff like that.

Judy