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

>>> Richard Knoppow <dickburk@ix.netcom.com> 08/19/04 5:04 PM >>>

----- Original Message -----
From: "Scott Wainer" <swphoto@verizon.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, August 19, 2004 1:07 PM
Subject: Re: New Cyanotype - my first unsuccessful attempt

> It may have to do with the chemical structure of the new
formula. As Dr.
> Ware points out in his book on cyanotype, the new formula
forms a lattice
> structure that can hold and bind other chemical molicules.
It may be that
> citric acid is retained and reacts with the chemistry or
the paper over a
> period of time and causes fading. Nitric and hydrochloric
acids might not be
> retained as strongly as citric acid and therefore cause
less fading. I am
> not a chemist so this is all conjecture on my part.
>
> Scott
>
>
   Well, I am NOT a chemist but Citric acid is a well known
sequestering agent so that might have some effect. Just a
guess. Lemon juice works well for cleaning mineral deposits
off pots and kettles, perhaps it also has an effect on
metals. In any case Citric is an organic acid and the others
are not, perhaps irrelevant.

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