Direct tannin process (no bleaching, no Potassium ferricyanide, just ferric oxalate/water and hydrogen peroxide + tannins)

Hi everybody, I want to share a new process, which involves direct "iron gall ink" print without the bleaching of cyanotype etc.

Short process description:
1. Sensitize suitable paper with ferric oxalate [only ferric oxalate, nothing else...]
2. Expose the paper under negative and UV light [UV light produces insoluble Iron(II) oxalate]
3. Wash the paper in water for couple of minutes [this removes remaining soluble Iron(III) oxalate, but the insoluble Iron(II) oxalate remains on the paper]
4. Oxidize iron using hydrogen peroxide (1-3%), couple of minutes... [to oxidize Iron(II) to Iron(III) ==> Iron(II) gal ink is soluble in water, and would be washed out, Iron(III) gal ink is not soluble, stays in paper...]
5. Quickly wash the paper in water to remove peroxide
6. Develop image in tannic acid bath (I am using sumac leaves, but any source of tannic acid/tannins should work similarly to toning of cyanotype) [this step converts the Iron(III) ions to insoluble iron gal ink and full image appears].

The attached photo shows result/test prints, on the top is the process described above (i.e. oxidation in step 4 using hydrogen peroxide, best result...), in the middle is step 4 oxidation performed using potassium permanganate (incomplete oxidation, manganese oxide stains etc...), and in the bottom the yellow/brown test print shows the iron oxidation using heat (in kitchen oven 30 minutes at 220 Celsius == does not work very well, the paper gives up before the iron... - this print is not yet developed in tannic acid bath show on the left).

Nice! I've wondered if there was an Iron gall-process.

There seems to be a threshold in the highlights. Have you managed to make a more linear print?

Thanks for sharing!

Interesting.

What concentration of ferric oxalate are you using?

This looks very promising. It would be interesting to see prints. Also, what concentration ferric oxalate are you using to sensitize your paper?

Wow, this is interesting for sure!

One thing that comes to mind is more of an amusing thought than anything serious for now - this reminds me of how paper is corroded/eaten away by iron gall ink. So I'd expect these prints over the course of a few centuries to disintegrate. Did you test that? Sorry - poor joke!

I really like that top print; it has good dmax, a fairly neutral black and shows very promising gradation indeed. Excellent work!

Very nice! Thanks for sharing your process.

Just a question on step #4 where insoluble Ferrous Oxalate is oxidised by Hydrogen Peroxide to Ferric Oxalate. But Ferric Oxalate is soluble and wouldn't the Peroxide bath as well as the subsequent wash (step #5) remove some Ferric Oxalate from the paper?

Welcome to Photrio!

p.s. how long does step #6 take?

fgorga said:

Interesting.

What concentration of ferric oxalate are you using

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The concentration is not critical for the process, but I used around 20% w/v.

koraks said:

Wow, this is interesting for sure!

One thing that comes to mind is more of an amusing thought than anything serious for now - this reminds me of how paper is corroded/eaten away by iron gall ink. So I'd expect these prints over the course of a few centuries to disintegrate. Did you test that? Sorry - poor joke!

I really like that top print; it has good dmax, a fairly neutral black and shows very promising gradation indeed. Excellent work!

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My understanding is that the paper is (sometimes) corroded/eaten by the sulfuric acid in the real iron gall ink (remaining after using ferrous sulfate as source of iron...)

Raghu Kuvempunagar said:

Very nice! Thanks for sharing your process.

Just a question on step #4 where insoluble Ferrous Oxalate is oxidised by Hydrogen Peroxide to Ferric Oxalate. But Ferric Oxalate is soluble and wouldn't the Peroxide bath as well as the subsequent wash (step #5) remove some Ferric Oxalate from the paper?

Welcome to Photrio!

p.s. how long does step #6 take?

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Remaining ferric oxalate is washed out in step 3 == in water, similarly to cyanotype... You need to use ferric oxalate, which after exposure produces insoluble Iron(II)oxalate. Other xxx ferric oxalates (e.g. potassium ferric oxalate, AFO etc) produce soluble iron(II) salts, and therefore cannot be used == everything would be washed out in step 3.

Very nice!

I think Raghu's question still remains... not sure why the ferrous oxalate isn't dissolving in the hydrogen peroxide solution. Or maybe "develop" tannins come before oxidation? Not sure.

NedL said:

Very nice!

I think Raghu's question still remains... not sure why the ferrous oxalate isn't dissolving in the hydrogen peroxide solution. Or maybe "develop" tannins come before oxidation? Not sure.

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There are two points:
1) ferrous oxalate is not soluble in water
And 2) it is actually questionable, whether the UV light produces ferrous oxalate at all == ferric oxalate has ideal formula Fe2Oxalic3, ie there is just 1.5 molecule of oxalic acid per 1 atom of Iron. After the UV destroys 1 molecule of oxalic acid only 0.5 oxalate ion remains per one iron == not enough to form ferrous oxalate (so ideally just 1/2 of the iron will be in the form of ferrous oxalate).

Similarly after you oxidize the iron(II) to iron(III) there is not enough oxalate ions to form (soluble) ferric oxalate.

Igor Jansen said:

There are two points:
1) ferrous oxalate is not soluble in water
And 2) it is actually questionable, whether the UV light produces ferrous oxalate at all == ferric oxalate has ideal formula Fe2Oxalic3, ie there is just 1.5 molecule of oxalic acid per 1 atom of Iron. After the UV destroys 1 molecule of oxalic acid only 0.5 oxalate ion remains per one iron == not enough to form ferrous oxalate (so ideally just 1/2 of the iron will be in the form of ferrous oxalate).

Similarly after you oxidize the iron(II) to iron(III) there is not enough oxalate ions to form (soluble) ferric oxalate.

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That's starting to make sense. I almost wrote my post differently and wondered if the hydrogen peroxide was making something other than ferric oxalate. Thanks!

Now I need some ferric oxalate to try this... going to go re-read Raghu's post about making it....

johnwwyatt said:

This looks very promising. It would be interesting to see prints. Also, what concentration ferric oxalate are you using to sensitize your paper?

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I have just couple, see attached, not a good negative (laser printer, there are spots, where the toner did not adhere well etc.), but it can give you an idea…

Igor Jansen said:

Hi everybody, I want to share a new process, which involves direct "iron gall ink" print without the bleaching of cyanotype etc.

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Very interesting and thanks again for posting. I have also played with similar ideas in the past, to no avail. I remember seeing this article, which I think may be similar.


A print process is described using ferric sulfate and oxalic acid as a two part sensitizer, that is exposed and then developed by potassium ferricyanide. Ferric sulfate is one of the chemical normally used for iron gall ink. I would think tannic acid may also develop that image, which is ferric hydroxide, I belive, which is what you have with a bleached cyanotype. I have those chemical, and would like to run down to my darkroom and try this, but everything is all down right now due to my UV exposure unit needing repair. I have those chemicals, but no ferric oxalate. Not to discourage the OP, but like I said, I have those chemicals.

Chemists can throw more light but the accounting of oxalate ions and the argument based on it is not correct. In the photo chemical reaction, there are two iron(iii) and three oxalate ions involved. One of the oxalate ions gets destroyed by UV light forming CO2 and donating one electron to each of the two iron(iii) which become iron(ii). The other two oxalate ions form Ferrous Oxalate with the two iron(ii). See https://www.mikeware.co.uk/mikeware/Iron-based_Processes.html

Now Ferrous Oxalate is oxidised by Peroxide to Ferric Oxalate which is water soluble. However, in you case, not much of it might go into solution at room temperature and with limited contact with water. There will be some movement of soluble iron(iii) which might produce stain or unclean highlights.

Igor Jansen said:

I have just couple, see attached, not a good negative (laser printer, there are spots, where the toner did not adhere well etc.), but it can give you an idea…

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Nice result! I've Ferric Oxalate and will give this process a try with Haritaki as I don't have Sumac with me.

Raghu Kuvempunagar said:

Chemists can throw more light but the accounting of oxalate ions and the argument based on it is not correct. In the photo chemical reaction, there are two iron(iii) and three oxalate ions involved. One of the oxalate ions gets destroyed by UV light forming CO2 and donating one electron to each of the two iron(iii) which become iron(ii). The other two oxalate ions form Ferrous Oxalate with the two iron(ii). See https://www.mikeware.co.uk/mikeware/Iron-based_Processes.html

Now Ferrous Oxalate is oxidised by Peroxide to Ferric Oxalate which is water soluble. However, in you case, not much of it might go into solution at room temperature and with limited contact with water. There will be some movement of soluble iron(iii) which might produce stain or unclean highlights.

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You are right. OP's process converts an insoluble ferrous image back to a soluble ferric image that would have an inherent disadvantage of image loss during the re-oxiadation process and while doing the subsequent toning with tannin - much the same way when Terry King first tried Cyanotype Rex with FAC having soluble ferrous which he eventually replaced with FO.

Perhaps if you skip the oxidation step and go straight to tannin bath, you would flip the image - i.e. insoluble ferric tannate where there is no exposure and soluble ferrous tannate where there is exposure which can be washed out. This would be a positive process. You will still be some contrast loss but it would be less than that introduced during the re-oxidation step. I think Jim Patterson over at altphotolist had something like this.

:Niranjan

nmp said:

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Perhaps if you skip the oxidation step and go straight to tannin bath, you would flip the image - i.e. insoluble ferric tannate where there is no exposure and soluble ferrous tannate where there is exposure which can be washed out. This would be a positive process. You will still be some contrast loss but it would be less than that introduced during the re-oxidation step. I think Jim Patterson over at altphotolist had something like this.

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I wondered if OP is somehow combining the oxidation and toning steps. Converting insoluble ferrous oxalate to insoluble ferric tannate. I'd be tempted to try putting the tannins in with the H2O2.

I don't have any ferric oxalate, or ferric nitrate to make some, but will be making an order from B&S sometime in the next few weeks and will get some to try.

Raghu Kuvempunagar said:

Nice result! I've Ferric Oxalate and will give this process a try with Haritaki as I don't have Sumac with me.

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Just as a first step you may try to expose paper sensitized only in ferric oxalate (which you have), expose it and wash in water == after this you will see the yellow image formed by insoluble iron(ii)…
The peroxide oxidation of this will give you darker brown/yellow image.

Ie for first test you don’t need tannic acid. Anyways, any source of tannins will work (coffee, tea…), just the final print will be not as black and whites might get stained etc…

NedL said:

try putting the tannins in with the H2O2.

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Neat idea. Worth trying.

Igor Jansen said:

Just as a first step you may try to expose paper sensitized only in ferric oxalate (which you have), expose it and wash in water == after this you will see the yellow image formed by insoluble iron(ii)…
The peroxide oxidation of this will give you darker brown/yellow image.

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I've done Cyanotype Rex with FO but never tried Peroxide oxidation but will try. If you get a chance, please consider posting the pics of the print after each step so that one can see what's happening throughout its journey.

Igor Jansen said:

any source of tannins will work (coffee, tea…), just the final print will be not as black and whites might get stained etc…

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Good to know this info. Coffee works for me.

NedL said:

I wondered if OP is somehow combining the oxidation and toning steps. Converting insoluble ferrous oxalate to insoluble ferric tannate. I'd be tempted to try putting the tannins in with the H2O2.

I don't have any ferric oxalate, or ferric nitrate to make some, but will be making an order from B&S sometime in the next few weeks and will get some to try.

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He is doing oxidation first and washing the peroxide before toning. Presumably, the washing is mild enough to not completely remove all of the now soluble ferric oxalate from the paper which is then subsequently paired with the tannic acid.

If you put tannic acid together with peroxide, would they not do redox with each other (former is a reducing agent.)

If you don't have ferric nitrate, you can use ferric sulfate or even ferric chloride to make in situ FO.

:Niranjan.

nmp said:

If you put tannic acid together with peroxide, would they not do redox with each other (former is a reducing agent.)

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That's true but some people add Peroxide to Cyanotype/Cuprotpye toners.

Raghu Kuvempunagar said:

That's true but some people add Peroxide to Cyanotype/Cuprotpye toners.

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They may be but to what end is not clear to me.

:Niranjan.

NedL said:

I wondered if OP is somehow combining the oxidation and toning steps. Converting insoluble ferrous oxalate to insoluble ferric tannate. I'd be tempted to try putting the tannins in with the H2O2.

I don't have any ferric oxalate, or ferric nitrate to make some, but will be making an order from B&S sometime in the next few weeks and will get some to try.

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I would not put the peroxide into tannic acid bath == hydrogen peroxide does not care what it oxidizes, most likely it would just oxidize the tannic acid bath well before you put the paper in…

The peroxide in higher concentrations destroys oxalic acid, so in the preparation of ferric oxalate from ferrous oxalate using peroxide and oxalic acid the peroxide must be added drop by drop with stirring.

nmp said:

...

If you put tannic acid together with peroxide, would they not do redox with each other (former is a reducing agent.)

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Oh yes, I think so. I was imagining mixing and using immediately. The question would be whether the oxalate reaction would happen or whether all the peroxide would be used up in other reactions. I've been playing with botanical cyanotype toners and with some of them you can visually see the liquid change color when exposed just to air. Annette Golaz says that higher pH promotes oxidation in the toners, so plays more of a role than just converting prussian blue.