It will probably work quite well, but you already know, that Copper Sulfate and Sodium Chloride are both very easily available and can be had for much less than 60 bucks per kilogram. This was most likely the key reason for using these two ingredients.
Copper Sulphate B&W Reversal Bleach
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Yeah, I’m just not super exited about trying to work with sulfuric acid. Hell, I’m not super thrilled about the Ammonia, but at least that is something I have experience with
Dumb question, but what is the sulfuric acid actually for? Is it there just to speed up the reaction of Copper Sulfate and Salt? Because that doesn’t make a whole lot of sense to be. Booth are aqueous, and their products are aqueous, so there isn’t really a reaction. Their ions just kind of hang out in solution.
You need to acidify the solution to get the bleach to work, it has nothing to do with the reaction between the copper sulfate and the salt. You need to get the pH low enough to cause the reaction to happen between the copper chloride and silver. Using copper chloride doesn't prevent you from needing to do that. If you don't want to use sulfuric acid (I don't blame you), start with the citric acid bleach I posted and see what you get. You may need a sulfite solution to completely clear it afterward, I don't know for sure.
An important factor is, that the bleach needs extra acidity upfront. You start the reaction with Cu2+ + Ag <===> Cu+ + Ag+, but then aerial Oxygen starts restoring the 4 * Cu+ + 2 * H2O + O2 <===> 4 * Cu2+ + 4 * OH-. This latter reaction would turn the bleach alkaline and thereby ineffective, at some point the copper would precipitate out. The extra Sulfuric Acid will gladly wait for all the OH- to come and thereby maintains the bleach.
PS: all those afraid of Sulfuric Acid: most of you drive around with at least a quart of quite concentrated Sulfuric Acid without much concern. Sulfuric Acid is a strong acid, but at 37% or below it will not jump at you, and it certainly smells a lot less than Ammonia.
PP: All those still afraid of Sulfuric Acid can use Sodium Bisulfate, which is a neat looking powder and even less scary than Sulfuric Acid.
PS: all those afraid of Sulfuric Acid: most of you drive around with at least a quart of quite concentrated Sulfuric Acid without much concern. Sulfuric Acid is a strong acid, but at 37% or below it will not jump at you, and it certainly smells a lot less than Ammonia.
PP: All those still afraid of Sulfuric Acid can use Sodium Bisulfate, which is a neat looking powder and even less scary than Sulfuric Acid.
Th
Thanks for the explanation. So even with pure CuCl2 with a ph around 3.5, this is still a concern, and you still need to be more acidic?
Also, here in CO at least, wet car batteries are not really a thing. They freeze in the winter, and die in like 2 years. The extra cost of dry cells is super worth it.
Thanks for the explanation. So even with pure CuCl2 with a ph around 3.5, this is still a concern, and you still need to be more acidic?
Also, here in CO at least, wet car batteries are not really a thing. They freeze in the winter, and die in like 2 years. The extra cost of dry cells is super worth it.
Battery acid in cars isn't that concentrated -- it's roughly 70% plain water. Still, plenty to eat holes in cotton fabric or make your skin itch even with airborne droplets.
You have to ask yourself: why is pH at 3.5 and who keeps it there? What happens, if I add a small amount of Sodium Carbonate to this solution?
The buffering most likely comes from the copper ions (Cu2+ + 2 * OH- <===> Cu(OH)2🠗), and these are exactly the ions you do not want to see buffering your solution. This is where you need a buffer. Strong acid also acts as buffer here, because it doesn't matter much, whether the pH is at 0 or at 2, as long at it stays somewhere down there.
PS: If your issue is specific to Sulfuric Acid: Hydrochloric Acid will work just as well.
PS: when I went to my chem store and asked for Sulfuric Acid, they gave me 37% Sulfuric Acid labeled as "battery acid". When I asked "what's the highest concentration you'd comfortably sell to an imbecile like me?", they suggested 15%. You can take this as hint, that 15% Sulfuric Acid requires no more respect and safe handling procedures than your typical print developer.
Good to know. If Kodak stop bath didn’t have an indicator dye, that would probably be perfect. Unfortunately, it does, and I would suspect that could stain the film.
This indicator dye will most definitely not stain your film. To my best knowledge it has never stained photographic paper either, unless you plan on drying that paper right after that bleach.
However, I have seen weird copper precipitates when I tried to acidify a copper sulfate bleach with Acetic Acid. It may not be acidic enough, or my Copper Sulfate was too concentrated. Copper Acetate is soluble, but not as much as e.g. Copper Sulfate. If you try this, use a small sample before you commit a larger batch of chemistry.
However, I have seen weird copper precipitates when I tried to acidify a copper sulfate bleach with Acetic Acid. It may not be acidic enough, or my Copper Sulfate was too concentrated. Copper Acetate is soluble, but not as much as e.g. Copper Sulfate. If you try this, use a small sample before you commit a larger batch of chemistry.
While still relatively soluble, I suspect that the precipitate is copper acetate. Silver acetate is less soluble. If this does work, you definitely need a sulfite clearing bath afterward to remove any silver acetate from the film. I don't know if that will also remove copper acetate. But any precipitate that forms from the copper is reducing the strength of the bleach as @Rudeofus referred to earlier.
Well, I have come up with a list of chemicals that I need to buy. Most I can get local, some I already have, but I still have 2 questions regarding chemicals:
1: is regular table salt OK for this? It seems like it has a bunch of other junk besides just NaCl. If not, would rock salt or sea salt work better?
2: I have Kodak Hypoclear, which is supposedly a good cleaning bath to remove stains that may show up. However, there is a giant crystal of what I’m assuming is the sodium sulfite. Any way to get it back in solution?
Thanks!
1: is regular table salt OK for this? It seems like it has a bunch of other junk besides just NaCl. If not, would rock salt or sea salt work better?
2: I have Kodak Hypoclear, which is supposedly a good cleaning bath to remove stains that may show up. However, there is a giant crystal of what I’m assuming is the sodium sulfite. Any way to get it back in solution?
Thanks!
Non-iodized table salt would be my preferred source of sodium chloride -- the "other stuff" that's in it is anti-caking agents which, in my experience (using it for things like salt prints) are photographically inert. The cheaper the salt, the less of that stuff is present, too; fifty cents a box is just right.
As @Donald Qualls said you need non-iodized salt and the "anti-caking agents" don't matter.
That will probably work. But, I do not know about getting a giant crystal back into solution. I would just get some sodium sulfite: you can get it from pool suppliers (used to bring chlorine level back to normal) or wine DIY shops. It's cheap and easy to get. You can even order it on Amazon. It's one of the most common chemicals in photographic home brewing so it will be useful for other projects.
Crush it as fine as possible, and use the hottest water you can manage to dissolve it. It'll be fine.
What's the concentration of this Hypoclear? Sodium Sulfite dissolves up to 200 g/l, and your Hypoclear should be much more dilute. The least soluble sodium salt, that you will regularly encounter in photo chemistry, is Sodium Bicarbonate (90 g/l @20°C). This can form easily in alkaline liquids rich in sodium ions, if they are exposed to air long enough.
In order to find out, what this lump of salt is, you can get it out of the liquid, rinse it briefly, then break off a small chunk, place it into a container, fill the container with deionized water high enough to cover the pieces. If the resulting solution smells like SO2, then it's Sodium Metabisulfite.
Then pour concentrated Citric Acid over it.
If it bubbles a lot:
- if it smells like SO2, then it's Sodium Sulfite
- if it's odorless, it's likely Sodium Bicarbonate
I would replace the liquid, unless this chunk of salt is either Sodium Sulfite or Sodium Bicarbonate.
He concentration of the Hypoclear is whatever 1 packet put into 1 gallon makes. Not much fancy mixing there.
Sorry, wasn’t clear enough. What I meant was “I am suspicious of spending time doing that”
Ah, I didn't realize this was a precipitate in mixed Hypo Clearing Agent solution -- I thought it was a lump in the powder. Given neither sodium sulfite in powder form nor commercial Hypo Clearing Agent is expensive (along with your suspicion) you're probably ahead to discard the solution and mix fresh.
If in fact I understood correctly the first time, the time required to crush the lump enough to dissolve shouldn't be much if you can get water into your darkroom at above 120 F. If you have ten pieces they'll dissolve in approximately (cube root of 10) the time the big lump would, and sodium sulfite normally dissolves pretty readily in warm water. If you can get water that's near boiling, the sulfite will dissolve even more readily.
If in fact I understood correctly the first time, the time required to crush the lump enough to dissolve shouldn't be much if you can get water into your darkroom at above 120 F. If you have ten pieces they'll dissolve in approximately (cube root of 10) the time the big lump would, and sodium sulfite normally dissolves pretty readily in warm water. If you can get water that's near boiling, the sulfite will dissolve even more readily.
Did you by any chance use a clearing bath? And do you (or anyone else) think that a clearing bath might help with this staining?
Yes, and yes, as mentioned above. Take a look at my blog post for the one I have used with the better peroxide bleach that contains citric acid.
I didn't see see any mention of a sulfite clearing bath, only ammonia, which is a part of the bleach, not a clearing bath. That’s why I asked. I’ll take a look at your blog post, though.
@MCB18 sorry, there are a lot of posts by now. This clearing bath will clear silver citrate. But by now I am not sure which bleach formula you intend to try (or already tried?). If you can give a summary of where things stand and what you are going to try, we can be more helpful.
Formula:
Formula:
- Water — 800ml
- Sodium sulfite — 20g
- Water to 1L
Ok, sorry.
I plan on trying the copper sulphate and salt bleach with citric acid as the acid lowering the Ph first. However, I was wondering if that yellow stain seen above would be removed with a sulfite clearing bath. If that yellow stain is Sodium Citrate, then it seems like the answer is yes. If it can be removed, then I would like to try the citric acid route first, and maybe I don’t have to use sulfuric acid in this process.
Ok, so like I said, there is no really paved path with that bleach yet: you will have to do some experimenting. I demonstrated that it works, but did not spend enough time to formulate everything to make clear slides yet. I don't think anybody will be able to tell you exactly what to do because of that.
As I mentioned, I think that that a sulfite bath will clear whatever staining is left, because I think that it is silver citrate that was not cleared by the ammonia. It *should* dissolve in the ammonia, so it could also be that I did not leave it long enough in the household ammonia. Or, I did not agitate enough. But if you find that you still have staining with ammonia alone, try the sulfite clearing bath I posted above. That is the one I used with the peroxide bleach that had citric acid and, following the instructions I posted above, it clears it.
I would plan on doing the following. This is for any reversal process that you haven't done before.
- Using your first developer to blacken down some 1/2 inch clips of film and then bleaching them back, redeveloping and fixing. You need to do this until you get the right times and procedures to get a clear strip out at the end. You will probably have to do this half a dozen times to get it right.
- Shooting 5 frames at a time at different exposures, snipping the film out the camera, and testing your full protocol. You will probably need to do this half a dozen times to get results that are good.
Alright, cool. I have a list of stuff I need, now I just need to get ammonia and copper sulphate. Ace Hardware has 10% clear ammonia, and copper sulphate as drain cleaner. A gallon of that should last a good long time, giving me 16 liters of 2.5% solution at least, and 2 lbs of copper sulfate should make lots of bleach, and probably some big crystals, too.
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