Re: washing/developing cyanotypes

Charles,

You don't mention which was printed first or if fresh water was used
between prints, etc. Could be the pH changed in the wash or perhaps the
peroxide exhausted and the lighter print will darken to match the other
in a few days.

I would suggest acidfying the first water bath with a small amount of
citric or acetic acid (stop bath, vinegar).

OTOH, maybe the 60-90 second difference in wash time did impact the
print. Time will tell...

Joe

>>> cryberg@comcast.net 11/15/05 11:22 PM >>>
    I've always considered the water bath after exposing a cyanotype to
be a
process of washing away the unexposed sensitizer in preparation for the
oxidation of the blue--which I always hasten with the short bath in a
weak
hydrogen peroxide solution. So I have never controlled it--when the
print
looks clear of yellow and stops running blue wash water I move it to
the
peroxide (my prints don't run as much blue as many have complained
about,
but there is some blue washoff).
    But today, trying to make two identical prints, I discovered that
one
was much darker than the other. Working backward, the only likley
possibility was a shorter water bath for the darker print. Obviously I
had
thought it was fully washed when I moved it to the peroxide, but,
equally
obviously, it wasn't. The difference has to be less than 90 seconds and
probably less than 60 seconds.
    The solution seems to be to time the wash length. Do any of you
need to
do this? Or have I overlooked some other possible cause? Needless to
say,
the exposure time and the sensitizer were as close to identical as can
be
controlled.
Charles Portland, OR
Received on Tue Nov 15 23:02:54 2005