B&W Reversal with Hydrogen Peroxide

relistan · Dec 13, 2020

That other thread linked above has a lot of focus on citric acid as a support for the peroxide, to remove free silver from the solution and keep the peroxide active. They even talk about using various acids that produce compounds with even less solubility. But the video I posted above uses vinegar (acetic acid). I found this chart about solubility of various silver compounds and it appears to me that acetic acid is much better for this: https://saltlakemetals.com/solubility_of_silver_compounds/ if I understand the process.

We don't want the new silver compounds to stay in the emulsion, we want them to dissolve so that they don't end up discoloring in the second developer. My guess now from a bunch of reading is that the staining that is left over even with acetic acid is still from some of those compounds remaining in the emulsion and developing in the second developer.

removed account4 · Dec 13, 2020

looking forward to your results using vinegar ...
I stick to simple, I have a ton of citric acid and peroxide is cheap and I have some of that rusty stuff so
for me I have no need to reinvent the wheel but im always excited to see people making easy no fuss no harsh chemical way of doing reversals.

Raghu Kuvempunagar · Dec 13, 2020

relistan said:
the staining that is left over even with acetic acid is still from some of those compounds remaining in the emulsion and developing in the second developer.

If it is a uniform stain that you get, then it is not a big concern - slides might look a little off-color but one can live with it. If the stain is uneven, then it can be ugly and distracting. Stains apart I would be concerned about incomplete bleaching with low strength bleach which results in muddy looking slides and blistering which kills the slides when it happens. I would also be concerned about the safety of using 9% peroxide with acetic acid.

relistan · Dec 13, 2020

I tried an experiment just now. I was thinking about how Oxy Clean type laundry stain products release hydrogen peroxide in solution. I looked at the tub of stuff we have around the house and it says it contains greater than 30% sodium carbonate peroxyhydrate. I thought why not test it out to see if that can work as a film bleaching agent. All the other discussions and the Kodak patent have acidic pH in the bleach and with all that sodium carbonate it would definitely be alkaline unless I balanced it with a fair bit of acid. I decided to try it anyway.

This is super preliminary, reasonably unscientific, but just to see "could it work".

I was thinking about an old thread where PE said a good way to test C-41 bleach was to take a black leader from a fully fixed B&W film and see if the bleach will fully whiten it. I have a trash can full of little bits of old film so I found some leaders and gave it a try. I tried just the stain remover by itself at room temperature but that didn't work noticeably. I tried it by itself at 120F, about as hot as you ever would want a film emulsion. That didn't do much after a few mins.

Then I started adding distilled malt vinegar (white vinegar is super hard to find here), a cap full at a time, and low an behold, it began to bleach. I suspect that it would work without, but it would have been quite slow and I don't know how fast it would exhaust. I'm working on really small pieces of film here so I also have no idea what the capacity is. However, it does work. See attached images.

What I got was a milky cream color of somewhat uneven looking distribution. I can see there was a fingerprint on the emulsion that prevented bleaching that section from working as well. I then put it into some fixer and it cleared down almost completely. However it left a brown stain. So the staining has nothing to do with the second developer.

The pH is still alkaline, I don't have a meter so I don't know what the pH is. But it still feels slimy to the touch, so I guess above 9 somewhere.

An attempt to re-use the bath that worked after it cooled resulted in no activity to speak of. Here's what I did:

300ml water at 120F
2 teaspoons of laundry oxy-clean type stain remover (14g)
5 cap fulls of distilled malt vinegar (40ml)
Stir it all up (it fizzes and bubbles a fair bit)
Immerse the film, let sit for 20 minutes with occasional stirring

Here's what I got. The right hand side is the bleached part. First pic is before fixer, second is after fixer. The mottling is at the border of where it was immersed and that part wasn't fully immersed.

This of course doesn't prove it's going to work for a whole roll of film, or frankly if it will work in a sealed tank. I suspect not. But it might work.

relistan · Dec 13, 2020

Raghu Kuvempunagar said:
If it is a uniform stain that you get, then it is not a big concern - slides might look a little off-color but one can live with it. If the stain is uneven, then it can be ugly and distracting. Stains apart I would be concerned about incomplete bleaching with low strength bleach which results in muddy looking slides and blistering which kills the slides when it happens. I would also be concerned about the safety of using 9% peroxide with acetic acid.

Yeah, agreed. If the stain is even you could called it "toned". I don't think I want to mess with 9% peroxide anyway, so I'll stick with the household stuff.

relistan · Dec 13, 2020

jnantz said:
looking forward to your results using vinegar ...
I stick to simple, I have a ton of citric acid and peroxide is cheap and I have some of that rusty stuff so
for me I have no need to reinvent the wheel but im always excited to see people making easy no fuss no harsh chemical way of doing reversals.

Thanks! Let's see if I figure out anything useful

Raghu Kuvempunagar · Dec 13, 2020

relistan said:
it contains greater than 30% sodium carbonate peroxyhydrate. [
This of course doesn't prove it's going to work for a whole roll of film, or frankly if it will work in a sealed tank. I suspect not. But it might work.

Percarbonate, the ingredient of your stain remover, and persulphate have found application in bleaching. Usually, one uses them with a bit of sulphuric acid. Haist discusses the use of these by themselves and with permanganate for superproportional and proportional reduction of density. They are not powerful enough for use in reversal processing at least in room temperature. To increase the effectiveness of persulphate bleach for reversal, ferric sulphate or ferric nitrate is added. There's a bleach known as Philip's Safe Solvent Bleach ( PSSB) used in holographic reversals that does just this. I've tried all these and found that it's more effective to use copper sulphate bleach for B&W film reversal if dichromate bleach is a strict no.

relistan · Dec 13, 2020

Raghu Kuvempunagar said:
Percarbonate, the ingredient of your stain remover, and persulphate have found application in bleaching. Usually, one uses them with a bit of sulphuric acid. Haist discusses the use of these by themselves and with permanganate for superproportional and proportional reduction of density. They are not powerful enough for use in reversal processing at least in room temperature.

Thanks for the good info. Well, that film was completely black and at 120 degrees F it was able to clear it entirely. I assume, hopefully correctly, that there is no other active ingredient doing the bleaching. Isn't its ability to fully bleach out a fully black section of film evidence that it is strong enough? It seems to work exceedingly well in my experiments. Here's another section of film, run in a completely newly mixed setup as I described above. Starting temperature 120F, no attempt to maintain temperature. Ending temperature 108F.

Here's the setup:

After 20 minutes of bleaching this is what I get:

I then redeveloped the tip of the film in paper strength Ilford Multigrade developer and it reblackened down fully. All of the film was then fixed. This is what I got (sorry for the different lighting. Compare film bases here):

Keep in mind that this is the end of a previously developed film and so the end of it is pretty beaten up from handling and having been in a waste basket for awhile. You can see at least one of my fingerprints. The brown stain is definitely not that bad and I think actually might be kind of nice in slides. Having now experimented with this a bit, I am starting to think that the stain is actually silver oxide. If that's right, then it seems to me (I'm not a chemist!) that the free silver being broken down from the halides by the peroxide is recombining with the peroxide to form silver oxide. If that's right, then it seems to mean that I need to add more vinegar to start with, to hopefully occupy more of the free silver before it can react with the peroxide.

Additional notes from further experimentation

DO NOT AGITATE This really seems to reduce the bleaching
Insert the film more or less right away. Do not wait for the bubbling to stop. It seems most active at the beginning and all other factors unchanged, waiting a couple of minutes makes it not work as well.
Make sure the vinegar is mixed and all the stain remover is mixed in. It can be hard to see because of all the bubbles.
The film will cover in bubbles. Do not attempt to remove them, they seem to be a good thing. Agitation or rubbing with a stir stick to remove bubbles seems to reduce bleaching.

I will continue to experiment with this, but I'm out of weekend. Luckily the holidays are coming and I have some time off... Next will be to attempt with actual photos.

relistan · Dec 13, 2020

Something I should point out that is not maybe that obvious above. The bleached and fixed film is a LOT clearer than the film base from my original B&W develop and fix. It's stained but density is a lot lower. I do not have a densitometer.

Raghu Kuvempunagar · Dec 13, 2020

relistan said:
at 120 degrees F it was able to clear it entirely.

The elevated temperature (~50C) and extended bleaching time (20 minutes) could be the reason why the bleach seems to have cleared the leader. Such high temperatures and long bleaching time can potentially be harmful to B&W film. But if it works for you, great! Will look forward to see more results and thanks for sharing experiences from a very interesting experiment.

relistan · Dec 13, 2020

Raghu Kuvempunagar said:
The elevated temperature (~50C) and extended bleaching time (20 minutes) could be the reason why the bleach seems to have cleared the leader. Such high temperatures and long bleaching time can potentially be harmful to B&W film. But if it works for you, great! Will look forward to see more results and thanks for sharing experiences from a very interesting experiment.

Thanks! Hey, it could all go bust when it hits real photos. Worth a shot anyway! I really appreciate your knowledge in this area.

YoIaMoNwater · Dec 13, 2020

I actually looked more into this yellow/orange phenomena because people in my biochemistry lab have used silver staining to detect proteins. Some googling showed that this is due to residual silver grain sizes.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC279568/

Check out the abstract and second paragraph under Discussion.

relistan · Dec 13, 2020

YoIaMoNwater said:
I actually looked more into this yellow/orange phenomena because people in my biochemistry lab have used silver staining to detect proteins. Some googling showed that this is due to residual silver grain sizes.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC279568/

Check out the abstract and second paragraph under Discussion.

Ah, very interesting. Thank you! So... for there to be silver grains present in order to form the stain, that implies that it was not quite fully bleached? That would help explain why the stain is higher under fingerprints as well.

YoIaMoNwater · Dec 13, 2020

relistan said:
Ah, very interesting. Thank you! So... for there to be silver grains present in order to form the stain, that implies that it was not quite fully bleached? That would help explain why the stain is higher under fingerprints as well.

Yea it definitely means bleaching isn't complete. I was wondering if you could play with the H2O2 concentration and see whether or not this helps. Just keep everything the same as you were doing before. I have to check what concentration we have in the lab and might give this a try as well.

relistan · Dec 13, 2020

YoIaMoNwater said:
Yea it definitely means bleaching isn't complete. I was wondering if you could play with the H2O2 concentration and see whether or not this helps. Just keep everything the same as you were doing before. I have to check what concentration we have in the lab and might give this a try as well.

Good to know! I am working with percarbonate here instead of peroxide. I have attempted to calculate the concentration of hydrogen peroxide present and I think it's higher than 3%. Here's my attempt at the math (not a chemist, correct me if I screwed this up):

I have 14g of stain remover, which claims "greater than 30%" concentration of percarbonate. If we assume this means effectively 30%, and we factor the amount of hydrogen peroxide by weight of percarbonate then we get:

14g * 0.3 * 0.325 = 1.3650 grams of hydrogen peroxide by weight

I might be showing my ignorance here but I believe that I can calculate that into the total volume (300 ml water + 40 ml vinegar—ignoring mass of acetic acid, assuming 100% purity) to get:

3.4 * 1.3650 = 4.6410%

I *think* I can do that because water is 1g/ml. I attempted to follow this without fully getting there: https://www.chemicalforums.com/index.php?topic=87407.0

So guessing that it's 90% pure, it's somewhere like 4.2% if I didn't screw anything up there.

YoIaMoNwater · Dec 13, 2020

relistan said:
Good to know! I am working with percarbonate here instead of peroxide. I have attempted to calculate the concentration of hydrogen peroxide present and I think it's higher than 3%. Here's my attempt at the math (not a chemist, correct me if I screwed this up):

I have 14g of stain remover, which claims "greater than 30%" concentration of percarbonate. If we assume this means effectively 30%, and we factor the amount of hydrogen peroxide by weight of percarbonate then we get:

14g * 0.3 * 0.325 = 1.3650 grams of hydrogen peroxide by weight

I might be showing my ignorance here but I believe that I can calculate that into the total volume (300 ml water + 40 ml vinegar—ignoring mass of acetic acid, assuming 100% purity) to get:

3.4 * 1.3650 = 4.6410%

I *think* I can do that because water is 1g/ml. I attempted to follow this without fully getting there: https://www.chemicalforums.com/index.php?topic=87407.0

So guessing that it's 90% pure, it's somewhere like 4.2% if I didn't screw anything up there.

Hey relistan, where did you get 0.325 from? 1 mol of sodium percarbonate gives 1.5 mol of H2O2.

Na2CO3 * 1.5 H2O2 -> Na+ + CO3^1- + 1.5 H2O2

If we assume 30% of stain remover contains sodium percarbonate (MW = 157 g/mol) then,

0.3(14 g)(1 mol/157 g) = 0.027 mol of Na2CO3

since it's 1:1.5 of Na2CO3:H2O2 then,

0.027(2) = 0.054 mol of H2O2

Mass of H2O2 is 34 g/mol then,

0.054 mol (34 g/mol) = 1.836 g of H2O2

If you're dissolving everything in total volume of 340 mL then,

1.836 g/340 mL = 0.5% of H2O2 solution, which is way less than the 9% used in the video.

I haven't done stoichiometry in years so someone else might want to check if this is right.

Edit: I just realized I messed up, it should be 1.5 instead of 2 at the 3rd step. Basically at the end it should be 0.75*0.5% so at 0.375%.

relistan · Dec 13, 2020

YoIaMoNwater said:
Hey relistan, where did you get 0.325 from? 1 mol of sodium percarbonate gives 1.5 mol of H2O2.

From that page I linked. It matches the (i know, not great source) Wikipedia article on percarbonate as well. 32.5% peroxide by _weight_. You are doing it properly with mass but I thought I understood from that linked article that it was diluted enough to be nearly the same.

But what I think I did wrong was multiply instead of divide If I do that properly, I'm much closer to your number (I think you are right). So, with my math, and assuming 100% purity, that ends up

1.3650 total / 3.4 because of water volume = 0.40%

YoIaMoNwater said:
I haven't done stoichiometry in years so someone else might want to check if this is right.

You seem to actually know how to calculate that so I'm going to assume you are right. If you want to double check that page I linked, maybe you can make better headway than I did.

This then makes me wonder why this works. Seems crazy low. He was using 3% in the video. Maybe it only works because it's such a short section of film and the peroxide doesn't exhaust. Or maybe it has to do with being so alkaline rather than acidic? I don't have a pH meter so I can't measure the actual pH but the liquid is slimy so definitely pretty alkaline, even with the vinegar added. Or maybe there is something else in that stain remover.

relistan · Dec 13, 2020

Thinking about what else might be in the stain remover to promote bleaching, I started looking at patents and came across this, which uses a manganese salt to activate percarbonate at "low" temperatures below 60 C : https://patents.google.com/patent/US6528470B1/en
https://patents.google.com/patent/US6528470B1/en
"As there is a decreasing trend in washing and cleansing temperatures worldwide due to environmental protection and energy conservation, there is interest in the development of bleaching activators that can exhibit bleaching power at even low temperatures."

EDIT: I bet there is a bunch of stuff in there, see this https://en.wikipedia.org/wiki/Bleach_activator

relistan · Dec 13, 2020

@Raghu Kuvempunagar I think the above might explain why it's outperforming percarbonate by itself.

YoIaMoNwater · Dec 13, 2020

relistan said:
From that page I linked. It matches the (i know, not great source) Wikipedia article on percarbonate as well. 32.5% peroxide by _weight_. You are doing it properly with mass but I thought I understood from that linked article that it was diluted enough to be nearly the same.

But what I think I did wrong was multiply instead of divide If I do that properly, I'm much closer to your number (I think you are right). So, with my math, and assuming 100% purity, that ends up

1.3650 total / 3.4 because of water volume = 0.40%

You seem to actually know how to calculate that so I'm going to assume you are right. If you want to double check that page I linked, maybe you can make better headway than I did.

This then makes me wonder why this works. Seems crazy low. He was using 3% in the video. Maybe it only works because it's such a short section of film and the peroxide doesn't exhaust. Or maybe it has to do with being so alkaline rather than acidic? I don't have a pH meter so I can't measure the actual pH but the liquid is slimy so definitely pretty alkaline, even with the vinegar added. Or maybe there is something else in that stain remover.

Dude I would definitely recommend you to NOT lower the pH.

Few years ago when I was trying to find a way to clean glass slides for microscopy experiments, the research papers I read all suggested to use a solution of sulphuric acid (concentrated, probably 98%) and H2O2 (30%) that basically eat away the glass surface. When I mixed the solution I accidentally spilled some on my lab bench and tried to clean it up with paper towels. This was a bad move because the moment the paper towel touched the solution it turned into a puff of black smoke and I inhaled a good amount of it. Basically the whole paper towel got combusted into pure carbon. This deadly mixture was called Piranha solution for a reason because the free radical oxygens it produces just "eats" everything away. I actually spilled some on my glove too and although there were no visible marks on my hand but the spot that I spilled on felt like a blister for weeks.

I know you're gonna be using diluted H2O2 from sodium percarbonate but it's the same principle and definitely something I wouldn't want to mess with again.

relistan · Dec 13, 2020

YoIaMoNwater said:
I know you're gonna be using diluted H2O2 from sodium percarbonate but it's the same principle and definitely something I wouldn't want to mess with again.

Scary story indeed. Yikes. I'm aware of how dangerous the oxidizing power of peroxide is. I am actually trying to stay away from anything dangerous. The Kodak patent here specifically says they targeted pH of 2-4 which is why I mention it. Presumably with a low peroxide concentration. But I think actually what may be going on here is different enough that this pH is not necessary or even desirable.

Raghu Kuvempunagar · Dec 14, 2020

relistan said:
@Raghu Kuvempunagar I think the above might explain why it's outperforming percarbonate by itself.

Bleach accelerators are definitely interesting in the context of reversal processing. I was searching one for copper sulphate and ceric sulphate some time ago. The problem with bleach accelerators is that they are not easily available, at least for me in India. And some of them are toxic. For example, the phenanthroline manganese complex accelerator for peroxide bleach in the patent you shared is toxic.

As far as percarbonate and persulphate bleaches are concerned, they have utility in the darkroom but they are not best suited for reversal processing. Only permanganate and dichromate bleaches have proven themselves to be really useful though permanganate can and at times damages the emulsion. Copper sulphate bleach also works fine but is very slow and is a two step process. There's a history of several decades of rigorous scientific research behind bleaches for reversal processing beyond the strawman efforts of hobbyists like me. Read Haist volume 2 for a detailed discussion on reversal bleaches.

relistan · Dec 14, 2020

I found the MSDS for this stain remover. They don't disclose anything other than sodium percarbonate and sodium carbonate. I'm not sure what the threshold is for needing to disclose agents. I assume something in trace amounts like that needed for an accelerant is not at the level to require it?

https://www.astonishcleaners.co.uk/...Active_Plus_Fabric_Stain_Remover_500g_SDS.pdf

Raghu Kuvempunagar · Dec 14, 2020

relistan said:
I found the MSDS for this stain remover. They don't disclose anything other than sodium percarbonate and sodium carbonate. I'm not sure what the threshold is for needing to disclose agents. I assume something in trace amounts like that needed for an accelerant is not at the level to require it?

https://www.astonishcleaners.co.uk/...Active_Plus_Fabric_Stain_Remover_500g_SDS.pdf

Depending on the brand, oxy bleach can contain some chloride apart from percarbonate and carbonate. Such a bleach might act as a partially rehalogenating bleach due to the presence of chloride and produce muddy slides.

relistan · Dec 14, 2020

Raghu Kuvempunagar said:
Depending on the brand, oxy bleach can contain some chloride apart from percarbonate and carbonate. Such a bleach might act as a partially rehalogenating bleach due to the presence of chloride and produce muddy slides.

Yeah, that makes sense. We'll find out when I try it. If it's not good it will have been a learning experience anyway.

B&W Reversal with Hydrogen Peroxide

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