Copper Sulphate B&W Reversal Bleach

[mohmad khatab]

How is this bleach?
Is it completely reliable?

 

[MCB18]

Thinking about trying this, I have a few questions though:

Does anyone have results fr the Copper Sulfate/Citric Acid/NaCl recipe?

And is the ammonia actually needed? If so, can I reuse it over multiple rolls? Thanks.

 

[relistan]

And is the ammonia actually needed? If so, can I reuse it over multiple rolls? Thanks.

The Ammonia is critical to the bleach. You are converting silver to silver chloride as the first step. In the second step you rely on the much better solvency of silver chloride vs silver bromide in ammonia. So the ammonia dissolves the silver chloride without taking away much of the silver bromide.

It is reusable a few times. Read the warning about too much silver build up earlier in the thread.

 

[MCB18]

The Ammonia is critical to the bleach. You are converting silver to silver chloride as the first step. In the second step you rely on the much better solvency of silver chloride vs silver bromide in ammonia. So the ammonia dissolves the silver chloride without taking away much of the silver bromide.

It is reusable a few times. Read the warning about too much silver build up earlier in the thread.

Thank you for clarifying. Some folks on a discord server are giving me crap for thinking this would work at all. But it seems like it should, so I might just try it.

About ammonia reuse, what should I look for when deciding if the solution can be re-used?

I am aware of the silver fulminate fears, but thank you for letting me know. I asked some folks that know much more chemistry than me about it. They said that although it is technically possible that it could form, it would be in such minute quantities that it wouldn’t be of any concern.

 

[Donald Qualls]

silver fulminate

Before you'd get enough concentration of "ammoniacal silver nitrate" in solution to form fulminating silver, you'd have to have silver nitrate (this is a big issue with mirror silvering solution as used to be used by telescope makers to coat their handmade focusing mirrors). From my understanding (and I'm far from being a chemist) the bigger concern in our case is ammoniacal copper forming due to carry-over from the copper sulfate bath, and that's pretty readily avoided by giving a wash step between those baths.

 

[relistan]

Thank you for clarifying. Some folks on a discord server are giving me crap for thinking this would work at all. But it seems like it should, so I might just try it.

It definitely works. I have used this bleach a few times. I just don’t have any scans to post. You can see that it works in Athiril’s first post on this thread.

 

[MCB18]

It definitely works. I have used this bleach a few times. I just don’t have any scans to post. You can see that it works in Athiril’s first post on this thread.

And are you using Copper Sulfate + NaCl + Citric Acid followed by household ammonia? If so, just a picture of the negatives would be appreciated, it doesn’t need to be super fancy.

 

[relistan]

And are you using Copper Sulfate + NaCl + Citric Acid followed by household ammonia? If so, just a picture of the negatives would be appreciated, it doesn’t need to be super fancy.

I experimented with citric acid but the only totally successful full reversals I did was with this bleach linked by @Raghu Kuvempunagar earlier in the thread https://real-photographs.co.uk/formulae/toners/copper-sulfate-bleach/

Yes, it’s household ammonia. My sulphuric acid was drain cleaner.

Raghu posted a couple of images on Flickr. Here’s one

If no one posts anything better I can go digging around in my negatives (positives?) over the weekend

 

[relistan]

I remembered that I had a semi-successful roll from the citric acid bleach in the drawer here. Quick snap to show that it does work, but I didn't finish work on a final bleach with citric acid. You can see there is still some staining and the Dmax is too low. The frame with my daughter looks much better, but I'm not posting that one. You can see the edge of it here to see how it looks. My household ammonia is 5% and I was diluting it 1:1 with water.

 

[MCB18]

I experimented with citric acid but the only totally successful full reversals I did was with this bleach linked by @Raghu Kuvempunagar earlier in the thread https://real-photographs.co.uk/formulae/toners/copper-sulfate-bleach/

Yes, it’s household ammonia. My sulphuric acid was drain cleaner.

Raghu posted a couple of images on Flickr. Here’s one

If no one posts anything better I can go digging around in my negatives (positives?) over the weekend

Alright, nice nice. Was hoping to use citric acid, as I don’t like the idea of Sulfuric acid. I would be afraid of it dissolving anything I have that would give me 6.5ml.

Is drain cleaner just sulfuric acid? I thought it had other things in it as well.

 

[halfaman]

Alright, nice nice. Was hoping to use citric acid, as I don’t like the idea of Sulfuric acid. I would be afraid of it dissolving anything I have that would give me 6.5ml.

There are diluted sulfuric acid presentations, from 25-50% that are less dangerous and easier to measure (6.5ml turns into 26ml of a 25% dilution).

 

[relistan]

Alright, nice nice. Was hoping to use citric acid, as I don’t like the idea of Sulfuric acid. I would be afraid of it dissolving anything I have that would give me 6.5ml.

Is drain cleaner just sulfuric acid? I thought it had other things in it as well.

I am pretty sure that with a little experimentation you can get citric acid to work. Was just showing that I hadn’t spent the time to formulate it just right. If you just want something that works, sulphuric is the easy route.

I can get drain cleaner here that is sulphuric acid. I don’t like that stuff much either.

 

[Rudeofus]

There are diluted sulfuric acid presentations, from 25-50% that are less dangerous and easier to measure (6.5ml turns into 26ml of a 25% dilution).

It could be quite difficult to get concentrated Sulfuric Acid, since it's acid (oh no! ), liquid (omg! ) and corrosive (help! ), and if that's not enough: terrorists have used it to pursue their misguided projects. Do yourself a favor and cancel all personal projects which really need it, and change all the other ones to use lower concentrations.

37% Sulfuric Acid on the other side is still acidic, liquid and corrosive, but at least not an ingredient of evil stuff, therefore it will be available everywhere as long as cars need starter batteries.

 

[Donald Qualls]

It could be quite difficult to get concentrated Sulfuric Acid,

Canada might be different, and EU surely is, but I bought concentrated sulfuric (sold as drain opener) in the Big Box store just a couple weekends ago. About $11 for a bottle that looks like a pint -- which at 6.5 ml at a time, is good for around fifty batches (it'll start to fail from water and CO2 absorption from air while the cap is open before I do that much reversal processing). Battery acid (30% strength) can be had at auto parts stores and I've used that for reversal bleach in the past.

BTW, the bottle this concentrate came in is plastic, probably polyethylene. An ordinary syringe ought to work for measuring, though the acid likely will degrade the seal on the plunger (rinsing it thoroughly immediately after use will help it last longer) -- or you could obtain a 10 ml borosilicate graduated cylinder for a few dollars; one of these can easily be read to half ml precision (and mixing bleach doesn't require high precision in measuring the acid anyway).

Sufuric acid, even concentrated, isn't the alchemical alkahest -- universal solvent -- it's "just" a strong acid. Lots of stuff is impervious to it, more takes relatively long exposure to produce significant degradation. It's only more hazardous than the lye I use to make Parodinal and DK-25R (to produce sodium metaborate in solution) in being a liquid instead of granulated.

 

[MCB18]

Alright. I have some disposable medical syringes that I can probably cut the needles off of and measure that way if it comes to that, or I might be able to ask some folks I know with battery backup systems if they have any. The one thing I would be concerned about with drain cleaner is that some brands I believe have dyes, and I don’t know if that would effect the film.

And you said that the bottle of drain cleaner degrades over time, so does that mean I need to get a fresh one? Or can I use some that I have on-hand and just use a bit more than 6 ml to make up for any list acidity?

BTW, I’m super sorry for the dumb questions, I’m just trying to figure this out, and also trying to be as safe as you can be while doing stuff like this.

 

[Donald Qualls]

the bottle of drain cleaner degrades over time, so does that mean I need to get a fresh one? Or can I use some that I have on-hand and just use a bit more than 6 ml to make up for any list acidity?

This is what I meant by not needing high precision in measuring the acid -- you probably don't need to compensate unless this bottle has been sitting for a long time since the seal was broken.

The acid in this bleach isn't properly a reagent; it's a buffering agent (against the weak alkalinity of the copper sulfate). The actual reaction is with the chloride donor, the table salt; the sulfuric acid just keeps the solution pH low enough for the copper to catalyze the sulfate to react with the silver, which then immediately forms insoluble silver chloride (so fast it precipitates where the silver metal was). As such, the amount of acid doesn't need to be very precise. Further, if it does degrade to the point where the pH begins to rise, the reaction will just slow down, and since this is done in the light, to completion, you can readily ensure that it's finished by adding time if needed.

 

[Rudeofus]

I would like to clarify two things here:

1. Carbon Dioxide will most definitely not degrade Sulfuric Acid in any way, shape or form. Any car battery lives for years, and if it fails, it doesn't fail because of Sulfuric Acid degradation. I have no idea, what could possibly have happened to your batch. You can watch, what Sulfuric Acid does to Carbon Dioxide by pouring dilute Sulfuric Acid into a large glass holding a small amount of sparkling water ;-)
2. Copper Sulfate is already acidic, but weakly buffered. Any alkali entering the bleach would likely raise pH. The most expected alkali is the Oxygen restoring the bleach by forming OH-[/SUP], but it can also come from carryover of a previous bath. The Sulfuring Acid keeps the pH firmly down in a range, where copper ions won't precipitate. One can call that buffering. I am not aware of any catalysis effect, though. It's the copper, which oxidizes the silver in this reaction, and the chloride shifts the reaction to the right by forming an insoluble compound.
   

 

[Donald Qualls]

Okay. I did say I'm not a chemist...

 

[MCB18]

Oh, ok. That helps a bunch! I can probably just use some PH paper to test the PH when the bleach is finished, and if I need to add a bit more sulfuric acid, I can add that… maybe. Adding acid to mostly water seems like a bad idea. So I’ll probably just put more than enough in there and hope the PH is low enough. And also that it isn’t too acidic, because IDK how that would affect the film.

 

[relistan]

Canada might be different, and EU surely is, but I bought concentrated sulfuric (sold as drain opener) in the Big Box store just a couple weekends ago. About $11 for a bottle that looks like a pint -- which at 6.5 ml at a time, is good for around fifty batches (it'll start to fail from water and CO2 absorption from air while the cap is open before I do that much reversal processing). Battery acid (30% strength) can be had at auto parts stores and I've used that for reversal bleach in the past.

In Ireland you cannot buy battery acid, but you can buy "professional" drain cleaner in the mini-sized version of big box stores which we have over here, which is 30% sulphuric acid. This is what I used.

 

[Donald Qualls]

"professional" drain cleaner

As long as you know what it is and how strong, you can make it work. Nothing I know of in photography requires undiluted concentrated acids (with the possible exception of making your own silver nitrate from metal -- and that wouldn't be sulfuric, would it?).

 

[relistan]

As long as you know what it is and how strong, you can make it work. Nothing I know of in photography requires undiluted concentrated acids (with the possible exception of making your own silver nitrate from metal -- and that wouldn't be sulfuric, would it?).

Yeah I was not arguing with you. I was pointing out the weird logic of what is allowed and not in various jurisdictions.

 

[Donald Qualls]

weird logic of what is allowed and not in various jurisdictions

Yep. Especially since a single YouTube search will find you at least one and possibly several videos on exactly how to convert drain cleaner sulfuric (diluted, dyed, chemicals added to "protect the pipes") to technical grade purity concentrated acid. Takes some lab glassware (all of which can be had from eBay sellers) and a heat source (like a plumber's propane torch, if you don't have a Bunsen burner). So anyone who wants con. sulfuric badly enough can get it...

 

[relistan]

I still had the bleach I last mixed up for this post . It has been sitting in a partially filled apple sauce jar for a year and three quarters. Today I did some printing and had one very dark print. I decided to try the bleach and it worked great. Bleached down a 5x7 print on Fomatone MG Classic in about a minute. So the keeping life of the citric acid version of the bleach is very good.

 

[MCB18]

Out of curiosity, could I just use Copper Chloride as a single ingredient? That seems like it could make things easier (albeit slightly more expensive).

I have also found that 50 g of CuSO4 and 20 g NaCl are both ≈0.3 moles, so unless there needs to be an excess of Cl ions, the recipe mentioned up thread doesn’t need as much salt.

With this knowledge, 50 g of copper (II) chloride dihydrate is almost exactly 0.3 moles. I can get 500 g for $30. Makes 10 L of stock solution, and 100 liters of working solution.

Please let me know if I have missed anything important, or did something wrong, as this is the first time I have actually applied anything I learned in chemistry to anything practical.