Camera Obscura

Cyanotype toning material

Aamon. Cyanotype toning: 5′ tannic acid 1%, 5′ ammonia 1%, 5′ acetic acid 0,1%. Dark points are inside the negative and do not depend from toning. Rives BFK Paper, 28×38cm. Image dimension 18×26cm.

I therefore used a digital negative with color and curve adapted to carbon print. Cyanotype requires a lower difference of density, which means that images printed with those negatives will have completely posterized and white light, a strong contrast and a marked grain. In this case, those defects are not frustrating. I can see how toning behave with completely white lights in zones that didn’t receive any exposition. Too high contrast compensates the toning flatness. Image grain can be amplified or reduced during the process, and this is interesting information too.

I used daemon pictures, the Mascarons du Pont Neuf of Paris, because their negatives have many transparent parts, so I do have large zones in prints where blue is the deepest I can obtain on cyanotypes. Negatives are exposed for 12 minutes, the reference exposition timing, that in my case gave the deepest blue I can achieve. A higher exposition blends shadows without augmenting dmax.

It is recycle paper, and those are the variables that I deliberately choose not to control. It is the back of some not successful gum prints, VDB or cyanotypes. It is a paper that already went under chemical and mechanical treatments. Some sheets are sized to gelatine and some no. Brands are from Arche Platine, Fabriano Artistico, Fabriano 50, Rives BFK, Canson “C” grain. Some cyanotypes, before toning, have been left for some days oxidizing, to obtain a definitive color, some other only a few hours.

Tannic acid is an old 1994 package. In every case, due to past experiences, I still haven’t seen big differences between tannic acid concentration and solution (except for the paper hue due to tea). So I’d say that the active ingredient is still quite functioning.

Kai Hamman cyanotype toning

Moloch. Complete cyanotype toning: 5′ ammonia 1%, 1′ acetic acid 0.1%, 5′ tannic acid 1%, 5′ acetic acid 0.1%. Bubble stains were present on paper even before printing the cyanotype and they do not depend from toning. Fabriano Paper Rives BFK, 28×38cm; image dimension: 17×26cm.

Kai Hamann published a toning procedure whom results, if not modified during scanning, are extremely astonishing. The reported examples have a pink hue that I easily recognize, some other are perfectly neutral, but most of all shadows have an intense and deep black, as far as in video some prints seem palladium ones or perfect Van Dyke Browns.

Resuming the procedure described on his site, Kai Hammann toning is the following: acetic acid 1%, water washing, ammonia 0,5% between 1 and 16 minutes depending on the required hue, water washing, acetic acid 1%, water washing, tannic acid 1% for some minutes, acetic acid washing 1%. At that time he suggests a method to control the final hue of the print, adding one more softly alkali bath after the last washing, but I didn’t explore this way because the last acid bath in Kai Hamann’s table seem having the most cold and neutral hues, whose I’m interested in.

Carrying out the procedure to the letter gave wonderful results, often with beautiful hues, but it was still impossible to obtain a black print and contain the dmax loss. Bleaching the image with ammonia gave prints with pink-browned lights and vaguely neutral shadows, something like black-purplish but absolutely not deep. Bleaching only a part of prints for some seconds, I obtain a familiar effect of warm gray high lights and purplish blue shadows, but even in this case I lose dmax.

Therefore the proposed toning technique doesn’t work for me. I do not know if it is due to the ammonia or tannic acid quality, water or –more probably- cyanotype formula and composition (ammoniacal ferric citrate is a bad defined compound and it varies from package to package).

Interesting collateral and useful information –long live serendipity!- is that the use of acetic acid bath, even if diluted, for example 0.1%, between alkali and tannic, sensibly preserves the bath itself from contamination. Bathing even only one picture directly from an alkalic bath to tannic acid turns this last into a brown compound and easily gets the paper dirty. In two or three images the tannic solution is practically useless. Even an intermediate water bath easily contaminates the tannic acid and the washing bath becomes toning itself, therefore it must be regularly changed. Acetic acid bath gets less dirty and most of all allowed the usage of tannic acid during the entire session without any visible alteration.

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