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.
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.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.
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.
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?
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.
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?
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.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?
I do not know about getting a giant crystal back into solution.
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:
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?
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 doesn't bubble, then it is something else.
- 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.
Crush it as fine as possible, and use the hottest water you can manage to dissolve it. It'll be fine.
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.
View attachment 328421
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.
@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:
Once bleaching is complete, you’ll run the film through this clearing bath for 1 minute 30 seconds to 2 minutes with continuous agitation.
- Water — 800ml
- Sodium sulfite — 20g
- Water to 1L
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.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.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?