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  1. #1
    Marco B's Avatar
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    Chemistry of tea-toning cyanotypes

    Although I haven't yet made any cyanotypes myself, I do like to read up on all kinds of stuff photography and alternative process related.

    One thing that struck me was the possibility of "(tea-)toning" cyanotypes. At first, my thought was that the process involved here, was nothing more than simply "dye-ing" the prints to lay a brown tea color on top of the blue. So not actually a chemical reaction transforming the cyanotype, but simply applying a kind of transparent "paint" layer. However, after reading Jason's article here on toning cyanotypes on APUG (archived article, was part of Article system on APUG before it was renewed), I was highly surprised and confused to see a "bleaching" step involved in the process, suggesting a chemical transformation of the Prussian blue pigment that forms the cyanotypes blue color, a much more complex process than I expected and similar to toning for example a silver image with sepia or selenium toner.

    So than, through some completely different search, I hit on this page about historically used "Iron gall ink", known for its corrosive and destructive properties on historical papers, sometimes completely eating through it:

    The ink corrosion website

    and especially:

    Iron gall ink - Chemical reactions
    Ink corrosion

    and I began to realize there may be a connection between the two. The iron gall pigment that colors the ink is made by the reaction of Fe2+ cation derived from Ironsulphate, with gallic acid or gallotannic acid (two different but related chemical substances, see links above), also called tannin, derived from galls.

    In this process, the iron cation binds in a chemical reaction with the tannin / gallic acid and / or gallotannic acid, to form the dark black/blue ferrogallotannate pigment, which gives the ink its black color.

    Now the process Jason described involved "bleaching" the Prussian blue of the cyanotype with sodium carbonate, an alkaline solution. Prussian blue is known to be broken down in alkaline conditions, probably releasing free Fe2+ cations (Cyanotypes consist of Prussian blue, which is a pigment with the chemical formula K+Fe3+[Fe2+(CN)6]-, also called ferricferrocyanide).
    The next step Jason described was using pure tannin (or tannin derived from strong tea) to tone the print, suggesting a similar reaction is involved as in the formation of the pigment that forms the color of "iron gall ink". The prussian blue of the cyanotype image is than (at least partly, depending on amount of bleaching), transformed to the same ferrogallotannate pigment created when making iron gall ink.

    I am surprised to see this process being a true chemical toning procedure... Are my conclusions right that the chemistry involved in producing "iron gall ink" and the "tea toning" of cyanotype are related?? Can someone confirm this?

    There is one difference though, for those who fear their "tannin/tea" toned cyanotypes may be as self-destructive as "iron gall ink" writing on paper. In the process of iron gall ink formation, excess ironsulphate can form sulphuric acid, and it is these excess remains and the acid formed from them that is thought to be the main culprit in the self-destructive properties of "iron gall ink" on paper, although the reactive and catalytic properties of free Fe cations seem to play a role as well. But no sulphate is present in the process of tannin/tea-toning cyanotypes...

    Marco
    Last edited by Marco B; 05-28-2010 at 06:45 AM. Click to view previous post history.
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    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

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    Marco B's Avatar
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    By the way, here is an example of the ink eating it's way through the paper of a historical document:



    Two additional remarks:

    - The formed ferrogallotannate pigment seems to be more light stable than the cyanotype blue, as the latter can suffer from a bleaching effect under light exposure, although this process is funny enough largely reversible by dark storage. See Mike Ware's literature on this (Google)

    - A calciumphytate treatment may help stabilize a toned print, by binding and removing any free Fe2+ and Fe3+ cations, see here and here for a more scientific article

    Marco
    Last edited by Marco B; 05-28-2010 at 06:43 AM. Click to view previous post history.
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    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  3. #3
    Chazzy's Avatar
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    Akki14 here on APUG has done some tea-toned cyanotypes, if you want to have a look.
    Charles Hohenstein

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    There are practitioners claiming they haven't experience any adverse effect (print fading and/or paper disintegrating) with prints bleached in alkali and toned with tannic acid *20 years ago*. Not a long time but a nice indicator OTOH; some web sources say paper will show signs of deterioration within years. Now, probably the chemistry is similar BUT toning a prussian blue image is way different than compounding iron-gall ink...

  5. #5
    Ole
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    Quote Originally Posted by Marco B View Post
    ... Are my conclusions right that the chemistry involved in producing "iron gall ink" and the "tea toning" of cyanotype are related?? Can someone confirm this? ...
    I think your conclusion is absolutely correct. That's probably why Lipton's Yellow is great for toning (un-bleached, in my case) cyanotypes, and completely unpalatable as tea (also in my case).

    An interesting experiment is to tone in a very tannin-rich red wine..
    -- Ole Tjugen, Luddite Elitist
    Norway

  6. #6
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    Quote Originally Posted by Ole View Post
    I think your conclusion is absolutely correct. That's probably why Lipton's Yellow is great for toning (un-bleached, in my case) cyanotypes, and completely unpalatable as tea (also in my case).

    An interesting experiment is to tone in a very tannin-rich red wine..
    So do you have any recommendations on a tannin rich red wine?

  7. #7
    Marco B's Avatar
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    Quote Originally Posted by Loris Medici View Post
    There are practitioners claiming they haven't experience any adverse effect (print fading and/or paper disintegrating) with prints bleached in alkali and toned with tannic acid *20 years ago*. Not a long time but a nice indicator OTOH; some web sources say paper will show signs of deterioration within years.
    Loris, thanks for the info, but you've slightly missed my point. If you read carefully, I didn't suggest tannic acid toned cyanotypes would fall apart within 20 years, or fade, rather, I even argued *against* it... And I also said cyanotypes have unique reversible fading, see Mike Ware's documentation of that (e.g. here: http://www.mikeware.co.uk/downloads/...Cyanotypes.doc and http://www.mikeware.co.uk/mikeware/main.html)

    And even iron gall ink documents show, according to the links I posted, a great difference in the degree of deterioration, depending not only on storage conditions, but also on the exact composition of the ink used. If the ink components (ironsulphate and gallic acid) were well balanced, with little excess ironsulphate, the ink can in fact be rather stable.

    Lastly, you have to remember that some of these documents are even centuries old...

    Quote Originally Posted by Loris Medici View Post
    Now, probably the chemistry is similar BUT toning a prussian blue image is way different than compounding iron-gall ink...
    Yes and no, I have shown or pointed out both the similarities (produces the same pigment), and the differences (different source components, no ironsulphate involved in cyanotype toning)

    Quote Originally Posted by Ole View Post
    I think your conclusion is absolutely correct. That's probably why Lipton's Yellow is great for toning (un-bleached, in my case) cyanotypes, and completely unpalatable as tea (also in my case).


    But you point out another good point, that is, tea-toning can be performed also without bleaching, but that is a completely different story, because in that case you don't have a chemical transformation, but just lay down an organic dye on top of the print. Per my initial thoughts of what tea toning cyanotypes meant.

    But I find it highly interesting to see and discover such connections between different stuff like ink for writing and toning of photographs...
    Last edited by Marco B; 05-29-2010 at 05:24 PM. Click to view previous post history.
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    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

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    Schlapp's Avatar
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    I don't believe non-bleached tea-toned cyanotypes are dyed since if you tone with white tea which has no effect on the paper, the tone of the blue does change - as it does also with green tea. If you print a light cyanotype which almost washes away then chuck it in green tea you can get a lovely delicate pink tone.
    I do hope I am not missing your point.

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    Marco B's Avatar
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    Quote Originally Posted by Schlapp View Post
    I don't believe non-bleached tea-toned cyanotypes are dyed since if you tone with white tea which has no effect on the paper, the tone of the blue does change - as it does also with green tea. If you print a light cyanotype which almost washes away then chuck it in green tea you can get a lovely delicate pink tone.
    I do hope I am not missing your point.
    No, and this is extremely interesting to hear. It can mean two things: a cyanotypes has some excess free Fe2+ cations available to react with tannic acid to create the ferrogallotannate pigment, which may not be so unlikely by the way, or there is some additional (breakdown) process in the cyanotype going on when in tea that I don't completely understand...

    Again, my current knowledge of cyanotype printing and toning is just theory, so I highly appreciate comments like yours from people who have actually worked with it... until I can try it out myself!
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  10. #10
    Marco B's Avatar
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    Quote Originally Posted by Schlapp View Post
    If you print a light cyanotype which almost washes away then chuck it in green tea you can get a lovely delicate pink tone.
    By the way, if you do know an example image on the internet of such a pink tone cyanotype, I would love to see it! Please post a link here in the thread if you can!
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

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