eaglewings35 said:
rickbb said:
Bleach works well for small amounts of film. The action of dissolving the protein based emulsion converts the bleach into lye and the reaction slows dramatically. Many methods use lye with bleach added to speed up the stripping process.
These are well known processes and the forum has lots of posts/information on them.
The last batch of x-ray film I did, (2 years ago as my last source finally went digital), I took the stripped sludge and put it in straight bleach to do a final dissolve of the remaining emulsion. Then was able to do a wash and filter to get clean silver salts without having to roast off any emulsion.
Hey Rick,
I've been doing some stripping of totally green industrial x-Ray film.
I bought some thiosulfate to strip the silver and emulsion from the plastic film.
Then I use HCl to convert the suspended silver to silver chloride, then I use iron (nails) to convert it to silver metal. The problem I've been having is at the end of the conversion. The silver chloride has converted to the fluffy grey (concrete color) silver material that is ready for washing and melting. Now for the problem area..... after I do several HCl rinses to make sure the iron is all gone, then I do several boiling water rinses.
I put the silver mud in the oven to dry it. Once I get it out, it has turned black.
Is this the result of the protein emulsion that coats the silver on the film? How is the protein emulsion dealt with? It affects the melt too. It causes a nasty smell, and even nastier melt,
Leaving a black layer on the silver. What's your take on this?
You appear to have mixed up bits and pieces from several different methods. Stop. You are making it hard on yourself. Recovery of silver from x-ray film is simple, labor intensive, but simple.
Thiosulfate only dissolves the undeveloped silver, not the emulsion so you should not have any in your mud to worry about. It will not dissolve any exposed and developed film either, you will need a different method if you get any of that.
If you have sufficient volume of film you should look at either buying or making an electrolytic recovery unit. It will plate out the silver directly from the thiosulfate as almost pure metallic silver ready to wash, dry and melt. A good setup will run automatically allowing you to do other things. If you have a good steady supply of film it will pay for itself very quickly, trust me.
If not then you can drop the silver from the thiosulfate with iron, zinc or copper. That dropped "mud" is silver sulfate, take that well washed mud and put in a solution of lye and slowly add corn syrup with continuous stirring, (this will stink to high heaven, but it's not toxic just smells like it). That will convert the silver sulfate into metallic silver. Thoroughly wash that mud, dry and melt.
You don't use HCL and iron to convert silver chloride to metallic silver, you use sulfuric acid and iron, (nails). I'm not sure you even had silver chloride to start with, you had silver sulfate and put that in HCL, maybe that made it silver chloride, I don't have enough chemistry background to know if works that way. But, you don't need to do this step in the first place so don't do it.
If it's fluffy gray it's not metallic silver it's possibly silver chloride and if you try and melt that directly you will lose some silver and make some noxious gasses in the process as well.
You can melt it, if you want to, but you need to add some flux, a pinch of borax and sodium carbonate. That will be a gray green mass on the silver button/bar that you can knock off with a hammer. But if you simplify your process and make actual metallic silver in the first place you won't need to do this either.
I don't know what that black layer is your getting, doubt it's any part of the emulsion as you shouldn't have any in the mud. I suspect it's an artifact of blending parts and pieces of different, (and not compatible), processes. That smell you are getting when you melt silver chloride is a toxic gas, hope your doing this outside and you stay upwind of it.
