Re: New Cyanotype - my first unsuccessful attempt

From: Richard Knoppow ^lt;[email protected]>
Date: 08/20/04-12:43:51 AM Z
Message-id: <003301c48681$4c3b89d0$aa685142@VALUED20606295>

----- Original Message -----
From: "Joe Smigiel" <>
To: <>;
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,
> 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
> 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
Received on Fri Aug 20 00:45:52 2004

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