Re: Contrasty Cyanotypes
James Luciana (luciana@ny.frontiercomm.net)
Mon, 24 Feb 1997 18:01:28 -0500
At 09:44 AM 2/24/97 -0800, you wrote:
>I spent last weekend making my first cyanotypes. Before starting, I read
>the relevant sections of Keepers of Light and read just about every
>posting on cyanotypes and enlarging negatives in the alt-photo archives. I
>didn't expect to get perfect prints my first try, but the problem I'm
>having is the opposite of what I'd expect. My cyanotypes are extremely
>contrasty, much more contrasty than silver gelatine prints of the same
>images. Isn't cyanotype supposed to have a longer range than silver? I get
>about 7 steps of a Stouffer 21 step to print.
>
>I'm using the Photographer's Formulare cyanotype kit, which uses the same
>formula as in Keepers of Light. I'm printing on Arches Cover. I'll try
>other papers to see if my results change. Does anyone have any suggestions
>as to what I might be doing wrong? Oh, my prints took about an hour to
>expose in Seattle's February sun. Isn't this a bit long? Any less, and my
>highlights washed away.
>
>Ron Connelly
>
>
Ron, it seems as though lots of people recommend a somewhat contrasty negative
for cyanotype, but it is my experience (both personally and in my classes at
ICP) that a somewhat flatter and thinner negative will work best to give you
information accross the scale from highlight to shadow. I usually make negs
with
a density range of about 1.1 and even less (for cyanotype) and I find they
give me
good dmax and detail in the highlights. Student work seems to bear this out.
The following seems to be what happens when you prepare and expose a
Cyanotype print:
Light strikes the ferric ammonium citrate in the presence of an organic
substance (most typically the sizing present in most papers).
This exposure to light reduces the ferric salts to ferrous salts.
Ferrous salts are capable of reducing other metallic salts.
After the ferric ammonium citrate is reduced to a ferrous salt, it in turn
reduces (breaks down) the potassium ferricynide in the solution to produce
a precipitate of an insoluble blue pigment. Areas not reduced (not exposed
sufficiently) remain in their ferric state and are washed away.
Note: If a certain paper doesn’t seem to “hold” the emulsion, it is
because it lacks appropriate sizing and so lacks the organic element of the
process necessary to reduce the ferric ammonium citrate from a ferric to a
ferrous state.
You may have a combination of a contrasty negative and the "wrong" paper.
And an hour in February? I'm not at all surprised, although I understand
Dr. Ware's
new cyanotype process is considerably more sensitive. I have some but
haven't had
an opportunity to work with it yet.
Good luck,
James