Re: New Cyanotype - my first unsuccessful attempt

----- Original Message -----
From: "Joe Smigiel" <jsmigiel@kvcc.edu>
To: <dickburk@ix.netcom.com>;
<alt-photo-process-l@sask.usask.ca>
Sent: Thursday, August 19, 2004 5:39 PM
Subject: Re: New Cyanotype - my first unsuccessful attempt

> I don't recall the original poster's message, but I might
suspect the
> issue has something to do with the paper and buffering.
Perhaps the
> nitric and sulfuric acids, being stronger, are more
efficient at
> removing any buffering agent in the specific paper being
used. The
> weaker citric acid may just not be strong enough to keep
the paper
> acidic and so fading occurs and is accelerated compared to
the other
> flavors.
>
> At one point in the discussion someone mentioned being
able to print on
> butcher's paper and it sounded like they were almost
surprised at this.
> IME, printing on very cheap papers such as that mentioned
(and paper
> bags, unbuffered papers, etc.) with the cyanotype process
is easily
> accomplished. It is the higher quality artist's papers,
especially
> those labelled "acid-free," which are difficult to make a
good blueprint
> upon.
>
> All this is just a guess on my part but perhaps one of the
chemists on
> the list could relate the relative pHs of the various
acids mentioned
> and whether a particular choice might adversely influence
the fading of
> the image as well as the longevity of the paper
substrates.
>
> Joe
>
>
   O.K., this now makes some sense. Acid-free papers are
often buffered alkaline to neutralize acides which might
form or be absorbed later. As you know Cyanotype tends to be
bleached by alkaline solutions. Even Iron-Blue toner for
silver gelatin paper must be washed in acidified water if it
is not to bleach. I think perhaps you are on the right track
to think that the stronger acids may be needed to overcome
the alkaline buffer in the paper.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com