Re: old vs. new cyanotype

Hi:

I've been working on summarizing things from Ware's cyanotype book -but
this is too much.

I'll do an essential summary of the chemical differences between classic
and cyanotype II.

First - Ware states that cyanotype or prussian blue is a chemical
structure with some variabilty, depending on how it is prepared. Its a
squarre crystal lattice with some variabilty as to what is in the lattice.

The lattice structure itself is capable of containing other compounds.

The classic cyanotype forms a crystal lattice that contains pottasium
within the lattice. This structure suffers from what is called
peptization. Peptization is the formation of a suspension of very fine
minute particles in water.

classis cyanotype does not really disolve in water - it is a very fine
suspension of fine particles. The particles are so small that they cannot
be seen - so it appears that they are dissolved, but they are not.

Apparantly these particles are so fine that they often do not bind to
paper - they wash away in the processing. Ware recommends the use of the
surfactant tween - presumably to aid in the binding of classic cyanotype
particles to paper.

Cyanotype II creates a form of prussian blue without significant
pottasium in the crystal structure. It does not suffer from petisation to
the same extent as classic cyantype. The reason that it is fiddly to
create is that one of the reactants (don't recall the name offhand) is not
commercially available. The process of heating up solutions and filtering
them creates the necessary compound for cyanotype II.

Cyanotype II presumably is better able to bind to paper than cyanotype
classic.

I would guess if you are able to do classic cyanotype without significant
image "washing away" in processing, then cyanotype II holds no advantage.

If you have a paper that you have to use and classic cyanotype washes
away, try cyanotype II - but maybe try adding some tween to classic
cyanotype first.

Gord

On Fri, 11 Jun 2004, Christina Z. Anderson wrote:

> A while back we were discussing the two cyanotype formulas. I reported this
> weird thing happening with the new cyanotype: the print would look perfect
> but all highlights would be lavender. I thought my solution was fogged, so I
> ordered a new batch from Photographer's Formulary.
>
> I mixed up the solution yesterday. I do say it is way more work to mix than
> the traditional formula, but still, manageable. The Formulary kit is so
> wonderful because everything is measured out in packets for you. $20 for
> 100ml.
>
> You have to heat distilled water, add the green crystals of ferric ammonium
> oxalate, pour in the bottle of dichromate solution, and then (the only putzy
> step) grind up the potassium ferricyanide crystals to a yellow powder. This
> I do by leaving it in the bag it comes in, and rolling it with a rolling
> pin. No mess, no dust. Then you have to add this to the mix and let sit in
> the dark for an hour. Then pour it thru a coffee filter and add water to
> make 100ml. Not bad, but still, one vote pro traditional.
>
> My old (very) solution was not fogged, because I still got the lavender
> highlights. I figured out what it is, too. Luckily I was making salsa.
> Not having my photo chemicals here, I squeezed some lime juice onto the
> lavender highlights and presto, they turned blue. Thus, the lavender is
> exposure, but in an alkaline environment. I feel like the Martha Stuart of
> kitchen photography.
>
> Hence, Fabriano Artistico is probably not a suitable paper for the new
> cyanotype unless you dink around somehow. I tried coating it with oxalic
> acid before printing, and that did not work. One more vote for the
> traditional.
>
> Other than this, still no wash off, still deep blue, still looks perfectly
> fine under tricolor gum, because the acidity of the dichromate in the gum
> layers must do what the lime juice did, takes care of the lavender.
> Chris
> PS BTW, Tom Ferguson, even with the paler nickel titanate layer in the Wang
> process, as opposed to the cadmium yellow, I still did not need to reprint a
> yellow layer--it was plenty yellow.
>
>

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Gordon J. Holtslander Dept. of Biology
holtsg@duke.usask.ca 112 Science Place
http://duke.usask.ca/~holtsg University of Saskatchewan
Tel (306) 966-4433 Saskatoon, Saskatchewan
Fax (306) 966-4461 Canada S7N 5E2
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Received on Fri Jun 11 09:49:40 2004