Re: New Cyanotype - my first unsuccessful attempt

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, August 20, 2004 10:21 PM
Subject: Re: New Cyanotype - my first unsuccessful attempt

> From: "Christina Z. Anderson" <zphoto@bellsouth.net>
> Subject: Re: New Cyanotype - my first unsuccessful attempt
> Date: Thu, 19 Aug 2004 14:36:59 -0400
>
> > Next question; why, do you think, or any chemists have a clue, would
> > citric acid cause fading but not nitric or hydrochloric?
>
> Sorry to make it boring, but this seems to be something that should be
> verified for its repeatability first. As far as I saw in this thread,
> there was one anecdotal report and we aren't very sure if this is real
> and indeed citric acid and light are involved.
>
> A test would be something like this. A piece of cyanotype should be
> exposed as evenly as possible (or better expose with 4 step wedges),
> process it as evenly as possible, and cut them in 4 pieces. Parts 1
> and 2 should be treated in citric acid bath and thoroughly
> washed. Parts 3 and 4 are just thoroughly washed. Parts 2 and 4 should
> be exposed to intense light while 1 and 3 should be stored in cool,
> dark place. If only part 2 loses its density appreciably while others
> are unchanged, the test is consistent with the anecdotal report. Then
> lack of fading with nitric acid should be tested similarly.
>
> There are dozen possibilities that can be argued but I don't think any
> of them is particularly likely.
>
> I routinely form Prussian blue at pH of 7.4. The specimen is stored
> and processed at pH 7.4 taking a few days. I keep those specimen in
> dark at room temperature, but they get exposed to intense light for
> microscopic examination occasionally. I don't read their densities
> because individual spots are very small, but I don't see any sign of
> fading or disappearing in a year or two. For that matter, people have
> used this technique for decades but I've never heard of an old
> specimen that went faded.
>
> --
> Ryuji Suzuki
> "You have to realize that junk is not the problem in and of itself.
> Junk is the symptom, not the problem."
> (Bob Dylan 1971; source: No Direction Home by Robert Shelton)
>
Received on Fri Aug 20 16:44:06 2004