Re: Cyanotype

[Loris Medici <mail@loris.medici.name>]

Thanks much Alberto for clarifying and refreshing our minds! Will save it
for future reference...

OTOH, I don't understand how those fine gram ratios are comparable since
FAC is ill defined and composition is pretty variable -> differs according
from supplier to supplier and even from batch to batch...

That's why I like much New Cyanotype (or POP Palladium which again uses
AFO instead of - AFC like, ill defined - FO): you deal with well defined
materials, you're sure you're mixing/usign the same stuff everytime.

Regards,
Loris.


29 Temmuz 2009, Çarşamba, 10:12 am tarihinde, Alberto Novo yazmış:
>> With the traditional Cyanotype
>
> I don't believe anymore that there is a traditional or classical
> cyanotype.
> Here are the compositions in g/100 ml in sol A:B and their ratios,
> gathered
> from different sources:
> 12.5:4.5 = 2.78 Wall (Photographic Facts and Formulas, 1924)
> 24:7 = 3.42 Namias (Chimica Fotografica, 1929)
> 36:16 = 2.25 Clerc (La Technique Photographique, 1950)
> 25:12 = 2.08 Glafkides (Photographic Chemistry, 1958)
> 22:15.4 = 1.42 Nettles (Breaking the rules, 1977)
> 25:25 = 1.00 Frederick (Creative Sunprinting, 1980)
> 20:8 = 2.5 Barnier (Coming into Focus, 2000)
>
> Note that the ratio 25:12 (Glafkides) is very close to the optimal ratio
> Fe
> am. citrate/ferricyanide which gives the maximun yield in Prussian Blue.
> Higher values (an excess of fe am citrate over ferricyanide, requested for
> the formation of Prussian blue) give more sensitivity but also bleeding.
> Lower values (an excess of ferricyanide) give no bleeding, lower
> sensitivity
> and more contrast.
> DMax is proportional to the amount of Prussian Blue, so I suggest to
> choose
> a formula with a ratio equal or lower than 2.08, possibly increasing the
> overall concentration. Cyanotype is also very sensitive to alkalinity in
> the
> paper (most of them are buffered with calcium carbonate) and in the water,
> so a first soaking (not more than 30") in acidic water is higly
> recommended.
>
> Alberto