Re: Getting back into Cyanotype (classic formula)

Christina,

When I first started reading about cyanotypes I noted "some" older formulas
used a ratio in the neighbourhood of 20% Ferric Ammonium Citrate (Part "A")
to 14% Potassium Ferricyanide (Part "B"). When I read some of the
contemporary A:B formulas were tapping the Pot. Ferr down to 8% I thought
this was, in effect, already going close to the 2:1 ratio people were
talking about being commonly used today. Maybe I misread. Maybe the purity
of older chemicals was different? I prepare my working solutions as 20% and
8%. And I do double coat. BTW, Ferric Ammonium Citrate seems to be very
soluble. I had no problem making a stock 40% solution. I'm guessing the
solubility is a little bit higher (50'ish perhaps?) So by doubling up your
20% you're essentially getting a 40% by of the Ferric Ammonium Citrate by
weight but you're increasing the overall volume of water in the emulsion as
well which is not the same as using a 40% soln.. Other than needing a bigger
bottle for Part "A" I don't know if having a "wetter" solution helps,
hinders or really matters. Bovine speculation perhaps ;^)

~m

----- Original Message -----
From: "Michael Koch-Schulte" <mkochsch@shaw.ca>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, February 11, 2006 11:46 PM
Subject: Re: Getting back into Cyanotype (classic formula)

>
> ----- Original Message -----
> From: "Christina Z. Anderson" <zphoto@montana.net>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Friday, February 10, 2006 2:31 PM
> Subject: Re: Getting back into Cyanotype (classic formula)
>
>
> > it works fine, Mac. weigh it and make a 20% solution, 20g to 100ml. I
> use
> > 8% pot ferri, but Sam Wang I think uses 10%. I also use it 2A:1B.
>
> Christina,
>
> Why do a 2:1 of part "A" to "B" why not just increase the weight by volume
> of part "A" or decrease the saturation of part "B". By going 2:1 aren't
you
> in effect just diluting part "B"? Q: Are you double coating this mixture?
>
> ~m
>
Received on Sun Feb 12 14:30:41 2006