Fuming Iron Blue Toner
From my last experiments at using iron blue toning to the moon series I produced some unsatisfying versions of the prints. The blue was overpowering and went across the entire image in an unaesthetic fashion. One advantage of iron toning, however, is that it is reversable with the application of a base such as ammonia.
(Note on Safety: I use household ammonia which is 30% concentration. I also use concentrated acetic acid. Undiluted they are each very powerful and can cause eye and other damage, as well as having strong fumes which are not healthy to breathe in. Not much is used, perhaps 5-10 ml but the area should be well ventilated to avoid getting overwhelmed by the fumes. Please take the necessary precautions.)
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| Example Blue Toned Print |
I considered restoring the prints to their original selves with an ammonia bath but struck on another idea. I have done fine woodworking over the years and there is an old technique for adding a patina to some wood called ammonia fuming. It works on wood with a lot of tannic acid such as oak (which can turn the oak almost black) or cherry where the reddish fresh wood gets a deeper brown color. The wood is placed in an enclosure with ammonia fumes which react with the tannic acid to give the desire patina. It seemed to me this should work with iron toning.
I made a simple fuming box with a darkroom tray, a sheet of Perspex as the lid, and a box of marbles to support the prints above the bottom of the tray. I use household ammonia (30%) and pour this into the tray, place the print on the box of marbles (marbles provides weight to keep it from floating). (Though you don't need too much ammonia.) then cover with the Perspex sheet to keep the fumes in. I do this quickly as the fumes are very strong and might be overwhelming.
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| Fuming Apparatus |
The Perspex allows me to watch the process and judge when to remove the print. One thing I like about iron toning is when I can get a less consistent toning across the image. It lends itself to a mixture of warm and cool tones and can look like dawn or dusk light.
This is what I got with one example. The blue toning dissipated closer to the edges in this case but left a core blue area of the sky. If I had left it in the fumes long enough the blue would have mostly disappeared. This is once again another manifestation of the serendipity of toning and Lith printing that can create some beautiful and mysterious images.
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| Ammonia Fuming Before (top) After (bottom) |
The sepia now appears almost pinkish in conjunction with the residual blue toning.
Another print where only the foreground was toned blue, I left in the fumes for 10-15 minutes and most of the blue had bleached away. The color moves towards a slate blue/gray as it fades. Again, before and after composite image.
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| Ammonia Fuming Before (top) After (bottom) |
More Experiments
Subsequent experimentation has determined that this fuming does not completely eliminate the blue toner like when the print is submerged in a dilute ammonia solution. I left a print in the fumes for several minutes and at one point the toning ceased to change and stayed consistent. I presume that the fumes cannot penetrate all of the dry emulsion, and this prevents complete bleaching of the blue toner.
Here is a sequence of lith developed images toned with iron toner, then fumed. This print is on Fohar Raster paper.
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| Original Lith Developed Image |
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| Iron Blue Toning |
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| Ammonia Fumed 'to completion' |
Here one can see the color shift associated with ammonia fuming. This process stops after a few minutes and does not seem to proceed any further despite continued exposure to the ammonia fumes. As hypothesized above it seems the ammonia fumes cannot fully penetrate the emulsion limiting the ability of the ammonia to eliminate all of the iron toning. (Lower down I disprove this assertion. Rather the fumes take an exceptionally long time to penetrate the emulsion see below...) At this point I thought perhaps if the emulsion is moistened this might allow the ammonia to fully penetrate the emulsion.
I soaked the fumed print in water for a minute or so then wiped all excess water off the emulsion. I then placed it back into the fuming box. Immediately the color changed almost to pink then disappeared altogether over the next minute. This seemed to prove the hypothesis. The result is below...
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| Ammonia Fumed with moist emulsion |
Long Period Fuming
I decided to explore longer time periods of fuming. Beow is another progression of prints taken from the lith print through iron toning and stages of fuming.
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| Original Lith Print |
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| Iron Blue Toning |
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| Initial Ammonia Fuming to completion (a few minutes) |
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| Further Ammonia Fuming (30 minutes) |
Longer fuming of 30 minutes deepened the color.
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| Overnight (8 hours) Ammonia Fuming |
This last one I left overnight in the fuming box. The paper was limp with the ammonia it had absorbed. Areas of the print had completely lost their toning, notably in the bottom and upper right where the original warmer tones existed. I suppose left even longer would have resulted in all the blue toning would have been lost.
Finally, as discussed below I tried acid fuming this print. I did see some slight color shift, but it took a couple of hours.
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| 2 hours acid fuming |
Iron Toning Chemistry
I tried to understand better the chemistry of what is happening in the process (UnblinkingEye). The basics of iron blue toning are as follows...
- Ferric ammonium citrate (green)
- Acid (Sulfuric, Oxalic, Acetic all mentioned in formulae)
- Potassium ferricyanide
The color that is imparted is Prussian Blue which is a produced by oxidation of ferrous ferrocyanide salts. The ferricyanide changes the developed silver in the print to silver ferricyanide (bleached silver which is colorless) and leaves the Prussian blue. At which point a short fix in weak fixer can brighten the color and remove the bleached silver, but this is optional and not universally recommended.
There is a separate formula for a clearing solution that helps clear the potassium ferricyanide staining.
Alkaline Effects
As mentioned before, the iron toner is very sensitive to pH. Alkalies (higher pH than 7) tend to 'untone' the image. Tap water tends to be slightly alkaline and so extended washing will change the color and eventually eliminate the Prussian blue. Alkalies convert the Prussian blue to hydrated ferric oxide lacks the blue color. Normal print developer is alkaline and has the same effect as well as converting the bleached silver back to silver.
This is the basis for shifting the color using ammonia fuming. Alkalies tend to shift color from cyan towards royal blue which is what is observed in the examples above.
Acid Effects
Some people give the final print a brief wash in slightly acid water to counteract the alkaline in tap water. I have not found this necessary and there is the risk the color returns to the cyan. For instance, a working strength stop bath is considered too acid for this purpose and dilution to 1/4 the strength is recommended. Of course, if there is a preference for a shift toward cyan this effect can be exploited towards that end.
This leads me to think that I could also try acid fuming. There are a few acids that have strong fumes, Hydrochloric, Acetic (vinegar), Formic (used for descaling). I am attempting to use Acetic acid to restore the blue toning from a print I used ammonia fuming to remove the color from.
Acid fuming restored slightly some of the cyan in the highlights but not nearly a complete restoration of the iron toning I was expecting. Below is the same ending print from above with complete absence of iron toning but now partially restored with acetic acid fuming. Note the color restores to the earlier cyan tone rather than the royal blue.
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| Fohar print from above series with acetic acid fuming |
Sepia on Iron Toning Effect
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| Iron Toned Test Print |
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| Sepia overtone |
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