B&W Reversal with Hydrogen Peroxide

relistan · Jan 10, 2021

kentanghk said:
The bleached strips were milky in my previous test and that's why I fixed them. I thought it was undeveloped silver halide but if the film bleached with peracetic acid bleach without EDTA did not turn black in second development, something else may be happening here.

View attachment 263433
Film strip after bleaching. It turned clear after fixing.

Ah you fixed them, right. Well the possibility remains that the sodium hydroxide I have is not pure enough since it's just from the hardware store. It may have nothing to do with EDTA. That's why I was thinking if you had time to check against your setup you could help control for anything wrong with mine. It definitely bleaches _differently_ with the EDTA in the bleach. The bubbles sort of flow together instead of one at a time.

I do have proper photo grade sodium hydroxide on order, but it's going to take a week or two to get here because everything ships so slowly from Europe now. I can't get anything from the UK because of Brexit. So many trucks are stuck waiting to go to Ireland and having to get through customs now that for example DPD has canceled shipping here from the UK for now

This is a little video I made of the bleach without the Adoflo, and with. This is the original bleach, not the EDTA version. Fomapan 400:

The first part of the clip shows the original bleach, with big bubbles that mostly stay on the film. The second clip shows the bleaching with Adoflo and the much smaller bubbles. Unfortunately I ended up with somewhat uneven bleaching from the second one. I will need to repeat on a larger piece of film to be sure.

I ran this setup on a clip of ADOX Silvermax and it does appear to reduce the larger blistering exhibited by that film. However, not enough.

kentanghk · Jan 11, 2021

relistan said:
Ah you fixed them, right. Well the possibility remains that the sodium hydroxide I have is not pure enough since it's just from the hardware store. It may have nothing to do with EDTA. That's why I was thinking if you had time to check against your setup you could help control for anything wrong with mine. It definitely bleaches _differently_ with the EDTA in the bleach. The bubbles sort of flow together instead of one at a time.

I tested a strip of ilford pan 400 and it did darken in second developer! I also bleached a strip in flexicolor fixer for comparison.

(Left: fixed only. Right: developed, bleached, second developed and fixed)

I measured optical density of the film strip.
Developed, bleached, second developed and fixed film 0.52
Fixed film 0.29

I have no idea what caused the darkening. Could it be some sort of re-deposition of developable silver compound back into the emulsion in the bleach?

relistan said:
I ran this setup on a clip of ADOX Silvermax and it does appear to reduce the larger blistering exhibited by that film. However, not enough.

That's interesting. How much Adoflo did you add?

Raghu Kuvempunagar · Jan 11, 2021

kentanghk said:
I measured optical density of the film strip.
Developed, bleached, second developed and fixed film 0.52
Fixed film 0.29

I have no idea what caused the darkening. Could it be some sort of re-deposition of developable silver compound back into the emulsion in the bleach?

Could be an issue of first developer not developing the highlights fully. Did you use a halide solvent in your first developer?

Raghu Kuvempunagar · Jan 11, 2021

kentanghk said:
I tested a strip of ilford pan 400 and it did darken in second developer! I also bleached a strip in flexicolor fixer for comparison.

Looks like there's no blistering in these test strips! Which specific bleach formula did you use for these test strips?

relistan · Jan 11, 2021

kentanghk said:
I have no idea what caused the darkening. Could it be some sort of re-deposition of developable silver compound back into the emulsion in the bleach?

That's interesting. How much Adoflo did you add?

That looks OK! I agree with Raghu that’s just not long enough in the first developer. Nothing like the problem I’ve had. I think it’s that my hardware store NaOH must have carbonate in it. If you develop longer in the first developer I think this will bleach down and redevelop clear! That’s encouraging actually.

As for Adoflo I added just one drop to 22ml of bleach. I bet 1 drop is enough even with more bleach.

kentanghk · Jan 11, 2021

Raghu Kuvempunagar said:
Could be an issue of first developer not developing the highlights fully. Did you use a halide solvent in your first developer?

I added thiosulphate to the first developer. I am still trying to figure out a proper developer formula and development time.
This is what I used:

D76 stock 1000mL
Sodium carbonate (anhydrous) 51.2g
Sodium thiosulphate pentahydrate 16g
Potassium bromide 4g

Raghu Kuvempunagar said:
Looks like there's no blistering in these test strips! Which specific bleach formula did you use for these test strips?

I used the EDTA-acetic acid-peroxide bleach formula from previous test.

Hydrogen peroxide (35%) 86.7ml/L
Glacial acetic acid 40ml/L
EDTA disodium dihydrate 0.57g/L

I let it sit for 3 days before using it. It appears to completely bleach the film in 3 minutes at 38C.

relistan said:
That looks OK! I agree with Raghu that’s just not long enough in the first developer. Nothing like the problem I’ve had. I think it’s that my hardware store NaOH must have carbonate in it. If you develop longer in the first developer I think this will bleach down and redevelop clear! That’s encouraging actually.

I think I will bleach a test strip with dichromate to confirm it's not a problem with the peroxide bleach.

relistan said:
As for Adoflo I added just one drop to 22ml of bleach. I bet 1 drop is enough even with more bleach.

Thanks! I can't get Adoflo here but I will try something with photoflo.

Raghu Kuvempunagar · Jan 11, 2021

kentanghk said:
I used the EDTA-acetic acid-peroxide bleach formula from previous test.

Hydrogen peroxide (35%) 86.7ml/L
Glacial acetic acid 40ml/L
EDTA disodium dihydrate 0.57g/L

I let it sit for 3 days before using it. It appears to completely bleach the film in 3 minutes at 38C.

Yes, this is essential for peracetic acid formation and consequent increase in the strength of the bleach. With proportionate increase in the concentrations of both peroxide and acetic acid suitably stabilized by EDTA, it would be nice if bleaching can be in done in 5-10 minutes at ~25C.

relistan · Jan 11, 2021

kentanghk said:
I think I will bleach a test strip with dichromate to confirm it's not a problem with the peroxide bleach.

Very good idea! That will help control for a lot of things.

kentanghk said:
Thanks! I can't get Adoflo here but I will try something with photoflo.

Yeah, I looked and they contain different ingredients, but the idea is the same of course. I have Kodak Photo Flo as well and can try that also. This was more of an idea I just had on the spot while looking at the bubbles and the Adoflo was sitting there

Raghu Kuvempunagar said:
Yes, this is essential for peracetic acid formation and consequent increase in the strength of the bleach. With proportionate increase in the concentrations of both peroxide and acetic acid suitably stabilized by EDTA, it would be nice if bleaching can be in done in 5-10 minutes at ~25C.

It is essential unless you have enough silver present in the bleach to catalyze the reaction. If you run a decent section of film through the bleach it forms peracetic acid in a very short time.

Testing with EDTA this weekend I had the re-development problem, but the bleaching was working well. I was seeing clearing times in the 5 minute time frame at 18-20C (room temperature at the time). I was using less acetic acid than @kentanghk, but I imagine that the times would be similar.

Raghu Kuvempunagar · Jan 11, 2021

relistan said:
If you run a decent section of film through the bleach it forms peracetic acid in a very short time.

Hmm.. I'm not sure this is indeed the case. The catalyst for peracetic acid formation from peroxide + acetic acid has always been dilute sulphuric acid in the literature, not silver. When silver is added to peroxide bleach, it acts as a catalyst for the decomposition of peroxide and releases a lot of oxygen. What you observed is mostly this, not per acetic acid formation. But who knows? Chemistry of peroxide + acetic acid bleach is quite complex and only someone who has done PhD level research on the subject can confirm for sure.

relistan · Jan 11, 2021

Raghu Kuvempunagar said:
Hmm.. I'm not sure this is indeed the case. The catalyst for peracetic acid formation from peroxide + acetic acid has always been dilute sulphuric acid in the literature, not silver. When silver is added to peroxide bleach, it acts as a catalyst for the decomposition of peroxide and releases a lot of oxygen. What you observed is mostly this, not per acetic acid formation. But who knows? Chemistry of peroxide + acetic acid bleach is quite complex and only someone who has done PhD level research on the subject can confirm for sure.

Raghu, I'm the one with the experiment in front of me. Try it yourself if you don't believe me. I am not arguing that sulfuric acid is a catalyst and that it is the way this is usually done: probably because it's much more efficient. But adding silver breaks down the peroxide and I am pretty sure that some of the free oxygen combines with the acetic acid to form peracetic acid. I have made at least 5 batches of this and seen this behavior now multiple times. It's slow on the first film and then faster right after, within minutes.

Raghu Kuvempunagar · Jan 11, 2021

relistan said:
Raghu, I'm the one with the experiment in front of me. Try it yourself if you don't believe me.

I think you misunderstood me. I never doubted your experimental observations. Apologies if I gave you that impression. The doubt I expressed was on your claim on per acetic acid formation with silver as the catalyst. Please note that peroxide bleach can itself oxidize silver without needing any peracetic acid to be formed. The presence of silver might have increased the oxidizing power of peroxide bleach by expediting the breakdown of peroxide into oxygen without involving peracetic acid. In other words, the chemical composition, oxidation reactions and strength of the bleach might not be the same if silver is added to the bleach. I hope this clears the misunderstanding even if you might or might not agree with me on per acetic acid formation.

relistan · Jan 11, 2021

Raghu Kuvempunagar said:
I think you misunderstood me. I never doubted your experimental observations. Apologies if I gave you that impression. The doubt I expressed was on your claim on per acetic acid formation with silver as the catalyst. Please note that peroxide bleach can itself oxidize silver without needing any peracetic acid to be formed. The presence of silver might have increased the oxidizing power of peroxide bleach by expediting the breakdown of peroxide into oxygen without involving peracetic acid. In other words, the chemical composition, oxidation reactions and strength of the bleach might not be the same if silver is added to the bleach. I hope this clears the misunderstanding even if you might or might not agree with me on per acetic acid formation.

Thanks for the follow up. I see what you are saying. I of course can't prove it is happening, but the bleach then behaves the same from then on.

After I posted I went to find this paper on the decomposition of hydrogen peroxide that I had read: http://www.proakademia.eu/gfx/baza_wiedzy/461/nr_26_45-52_2_2.pdf

They say: "Due to the heterogeneous nature of the process of decomposition of H2O2 catalysed by silver the exact mechanism of this reaction is still unknown, probably it is based on a radical mechanism."

From reading this: https://chem.libretexts.org/Bookshe..._of_Organic_Reactions/6.04:_Radical_Reactions I believe this is saying that what I think is happening is possible. That's not proof, but it seems possible.

YoIaMoNwater · Jan 11, 2021

kentanghk said:
I tested a strip of ilford pan 400 and it did darken in second developer! I also bleached a strip in flexicolor fixer for comparison.

(Left: fixed only. Right: developed, bleached, second developed and fixed)
View attachment 263508

I measured optical density of the film strip.
Developed, bleached, second developed and fixed film 0.52
Fixed film 0.29

I have no idea what caused the darkening. Could it be some sort of re-deposition of developable silver compound back into the emulsion in the bleach?

That's interesting. How much Adoflo did you add?

Like others have mentioned, it's likely that the film wasn't developed enough. I would keep everything in your work flow constant but increase the development time in increments. If that still doesn't solve the issue then it's likely that it's the film emulsion. I had a similar problem regarding TMax400, the film base itself is dark after second development (including the border markings).

Awesome work you and @relistan have done so far!

relistan · Jan 11, 2021

YoIaMoNwater said:
Awesome work you and @relistan have done so far!

Thank you! @kentanghk has been doing some awesome work here. Definitely appreciate the support from all you guys.

Good news... DHL claims that my 12% peroxide is getting delivered on Weds. We shall see.

kentanghk · Jan 11, 2021

The EDTA-acetic acid-peroxide bleach I prepared on last Friday died on me today. It did not bleach after 20 minutes at 38C. I had to add some 30% hydrogen peroxide to make it work again. Honestly I didn't expect it to have such short shelf life.

Well, the good news is that the darkening I encountered was likely to be underdeveloped silver in first developer. I increased the first development time to 20 minutes and the film strips bleached by dichromate and EDTA-acetic acid-peroxide bleach are virtually identical except for the slight staining in peroxide-bleached film.

relistan · Jan 12, 2021

kentanghk said:
The EDTA-acetic acid-peroxide bleach I prepared on last Friday died on me today. It did not bleach after 20 minutes at 38C. I had to add some 30% hydrogen peroxide to make it work again. Honestly I didn't expect it to have such short shelf life.

Well, the good news is that the darkening I encountered was likely to be underdeveloped silver in first developer. I increased the first development time to 20 minutes and the film strips bleached by dichromate and EDTA-acetic acid-peroxide bleach are virtually identical except for the slight staining in peroxide-bleached film.

Very interesting about the shelf life. I will try the small sample I mixed this weekend and see if it's alive.

That's very good news about the bleach, however! It means that I have some contaminant. Hopefully it's the sodium hydroxide and not the technical grade EDTA.

relistan · Jan 12, 2021

So I tested the EDTA/peracetic acid bleach today that I made on Saturday and it’s working! So @kentanghk it might be something else that is the issue? Was it in a sealed container?

kentanghk · Jan 12, 2021

relistan said:
So I tested the EDTA/peracetic acid bleach today that I made on Saturday and it’s working! So @kentanghk it might be something else that is the issue? Was it in a sealed container?

It was in a sealed glass bottle. I should probably use a brown bottle instead.

kentanghk · Jan 12, 2021

I developed a roll of ilford FP4+ with a new batch of EDTA-acetic acid-peroxide bleach. The reversal was sepia stained and flow marks/ incomplete bleaching was observed. There seems to be some blistering too but I'll have to check it with a loupe after drying to confirm.

I suspect low agitation is causing problems here. I got lazy and only agitated a few times during bleach. I did constant agitation in the phthalate-silver nitrate-peroxide bleach I tested years ago.

relistan · Jan 13, 2021

It was in a sealed glass bottle. I should probably use a brown bottle instead.

Huh, well mine was just sitting in a darkish room in a clear bottle. I wonder if my 3% peroxide has an acid preservative in it and that's what is keeping it around? Could also be what is contaminating my test.

kentanghk said:
I developed a roll of ilford FP4+ with a new batch of EDTA-acetic acid-peroxide bleach. The reversal was sepia stained and flow marks/ incomplete bleaching was observed. There seems to be some blistering too but I'll have to check it with a loupe after drying to confirm.

I suspect low agitation is causing problems here. I got lazy and only agitated a few times during bleach. I did constant agitation in the phthalate-silver nitrate-peroxide bleach I tested years ago.

Sorry to be slow to reply, busy day! Ah, bummer that it didn't work out the first time. Those flow marks that happen with the EDTA are interesting, I have seen them, too. I think you are right about agitation. What I found with the bleach without the EDTA was that it relies on a chain reaction and agitation kind of messes it up. But with the EDTA I think we do need to agitate a bit to make it work. I have not tried on a full piece of film because of the staining I'm getting with whatever contaminant I have. I was thinking about trying to put it into a sulfite clearing bath after the bleach to see if that will clear the staining. If that works, then I will try a full film.

How does the staining compare to your citric acid bleach? Were you able to look at them with a loupe and see what the blistering looks like? I wonder if a drop of Photo Flo would interrupt the flow marks?

relistan · Jan 14, 2021

I got ahold of some zinc sulfate (reagent grade) and will try out one of the Konica bleaches specified with that this weekend.

relistan · Jan 16, 2021

I tried various experiments today, with some success! I will post a more detailed update later this evening.

I did not make much headway with the peroxide/acetic acid/EDTA bleach, and adding Zinc Sulfate sped it up, but didn't seem to achieve much else.

However, peroxide/citric acid/EDTA/zinc sulfate looks promising.

I tried various combinations of things and the thing which has worked out so far is:

3% hydrogen peroxide — 20ml
Citric acid — 1g
12.8% solution EDTA — 1ml
Zinc sulfate — 0.2g
Sodium bicarbonate (yes, bi-) added to target pH a bit over 4 (pH paper)
20 minutes at 30C

Bleaching was slow, but *much* faster than without the zinc sulfate. I will try it with more added to see if this speeds it up. Most people are using 9% peroxide with citric acid but I don't have that available (yet). That would surely be faster.

Whatever problem I'm having adding EDTA to the acetic acid bleach, it's not that the EDTA is contaminted.

What I got was nice, clear film, no staining, no noticeable blistering, evenly bleached. I don't think I bleached it quite long enough but it looks good. I will post photos when dry. This seems promising.

Second win: the original bleach (peracetic acid) that only seems to work with Fomapan 400, also works beautifully with Ilford FP4. No staining, no noticeable blisternig. I will run a roll of it when I get time to do it.

relistan · Jan 16, 2021

Here's a shot showing the milky color of the bleach with the zinc sulfate in it. It definitely got a bit milkier with the bicarbonate added as well. The laundry pin is holding the film submerged vertically in the bleach, which is in an outer bath to help maintain the temperature at 30C.

This is the film after bleaching, before redevelopment. The spots are water spots, because it was not yet dry, obviously.

Here's after redevelopment and drying. I think it could have used a little more time in the bleach.

kentanghk · Jan 17, 2021

relistan said:
How does the staining compare to your citric acid bleach? Were you able to look at them with a loupe and see what the blistering looks like? I wonder if a drop of Photo Flo would interrupt the flow marks?

Citric acid bleach appears to produce less staining and better Dmax. I have no idea why the bleach can affect Dmax. Maybe the acetic acid bleach can actually bleach-fix as the Konica patent suggested?

The flow marks look really bad in acetic acid bleach. I might try adding some Photo-flo next time.

(left: acetic acid bleach, right: citric acid bleach)

And here is the blistering

relistan said:
However, peroxide/citric acid/EDTA/zinc sulfate looks promising.
What I got was nice, clear film, no staining, no noticeable blistering, evenly bleached. I don't think I bleached it quite long enough but it looks good. I will post photos when dry. This seems promising.

This looks really promising. I wonder if zinc can substitute silver in my citric acid-silver nitrate formula. It would be far cheaper and safer to make. I am having inconsistent results with acetic acid bleach so I might look more into citric acid instead.

I hope I can run some test this week if I have time. There is kind of a film shortage here in Hong Kong. I can't get any FP4 locally and to my surprise Kodak film is sold out in almost every shop here.

relistan · Jan 17, 2021

kentanghk said:
Citric acid bleach appears to produce less staining and better Dmax. I have no idea why the bleach can affect Dmax. Maybe the acetic acid bleach can actually bleach-fix as the Konica patent suggested?

This makes sense to me and matches my experience. Except for Silvermax, I was unable to put *any* solvent in the first developer without making it too thin when using the peroxide/acetic acid bleach. I do believe it has some fixing activity.

kentanghk said:
(left: acetic acid bleach, right: citric acid bleach)

Well the citric acid looks a lot better here. The interesting thing to me is that with only the vinegar/acetic acid I *usually* get no staining. I used to think staining was speed related but it's not at all.

kentanghk said:
This looks really promising. I wonder if zinc can substitute silver in my citric acid-silver nitrate formula. It would be far cheaper and safer to make. I am having inconsistent results with acetic acid bleach so I might look more into citric acid instead.

Yes! I think it can. The bleach is faster with it there. You will probably need noticeably more of it than you did silver nitrate, though. I tried it with just acetic acid today and will report about it below.

kentanghk said:
I hope I can run some test this week if I have time. There is kind of a film shortage here in Hong Kong. I can't get any FP4 locally and to my surprise Kodak film is sold out in almost every shop here.

Look forward to seeing any results you might have. Wow, didn't know it was so hard to get B&W film, also. I know that Kodak and Fuji consumer color films are close to sold out worldwide due to demand during the pandemic![/QUOTE]

B&W Reversal with Hydrogen Peroxide

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