Copper finishing problem

I know this may not be the exact newsgroup to post this question, but it's
the closest thing I found.
I have some very expensive copper cookware, and after using on the gas
range for some time, the copper of course oxidizes and darkens.
I tried to clean it with a mixture of vinegar and salt, and it removed the
oxidation, but I left the liquid on one of the items too long and it ruined
it: instead of mirror-shiny copper surface, it has milky-looking spots (the
vinegar itself started to get a green tinge).
How can I fix this? Is it possible to do chemically, or do I have to find
somewhere to repolish the item?
By the way, the salt I used is not regular but Half Salt (half normal salt
and half potassium salt).
Thanks for any advice or redirection to other sources of help.
Reply to
Prune
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This is exactly the right newsgroup.
I would use fine sandpaper to fix it. Maybe start with 400 grit and then go to even finer like 600 and then 1200. After that some brasso. You can get the fine sandpaper at auto supply stores and Walmart.
Dan
Prune wrote in message
Reply to
Dan Caster
It's probably just surface discolouration. I'd try rubbing with a pad of that stainless steel pan cleaner mesh or green nylon Scotch-Brite. You can shine it up again later with metal polish. Don't use abrasive paper unless you start with something really fine like 600 or 800 grit. You'll take forever to get the scratches out.
Dave Baker - Puma Race Engines
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Reply to
Dave Baker
snipped-for-privacy@aol.comma (Dave Baker) wrote in news: snipped-for-privacy@mb-m12.aol.com:
Thanks for everyone's replies. The Scotch-Brite doesn't take it off (maybe if I scrubbed for a few days non-stop :)), but if I use a piece of metal it's very easy to scratch off. So sandpaper would work, but the problem with that approach is that it will scratch it up too much (I did experiments on a sheet of copper and I can't get it as smooth as it was). Perhaps you guys can recommend some super fine abrasive polisher. Or perhaps I should find a professional to repolish the thing. I tried looking in the phonebook, but I'm not sure what to look for. I wonder how much can I expect to be charged. It's just that I'm afraid to make it any worse, since the retail price of the pot is about 400 USD and there's no chance of finding the kind of deal I did on eBay again :(
Reply to
Prune
What you need is a heavy duty buffer with a hard and soft buff and the right buffing compounds. This is what commercial chrome platers use on the copper under coat to get the mirror finish on the chrome plate. Google electro plating supplies
Reply to
Donald
What grades of sandpaper did you use? 1200 grit gets it pretty close. Between that and Brasso, you could use a buffing wheel and red rouge. I didn't mention that because if you had a buffing set up, you would not be asking the question.
Talk to you local jewelers and gunsmiths. Maybe the art teacher at the high school. If you have used 1200 girt sandpaper to get a uniform finish, it should only take a few minutes with a buffer.
Dan
Prune wrote in message > So sandpaper would work, but the problem with that approach is that it will > scratch it up too much (I did experiments on a sheet of copper and I can't > get it as smooth as it was). > Perhaps you guys can recommend some super fine abrasive polisher.
Reply to
Dan Caster
Stay away from any kind of abrasive. The best way is to use a pickle solution to clean the copper. Easy way is use 1 part sulfuric acid and 10 parts water. To find sulfuric acid go to the local auto parts store and buy battery acid. About $3. Just make sure you add the acid to the water. You could take an old rag and let it soak on the spots for about 10 minutes. The rag will fall apart from the acid. The copper will return back to raw copper state, a kind of pink or salmon color. Then use something like Twinkle for copper to polish up. By the way have you just tried using Twinkle for copper in the first place? Good luck and wear your rubber gloves, goggles, and take precautions with the pickle.
Reply to
Warren Townsend
If you want to dissolve the copper oxides I would suggest that muriatic acid is a better choice. You don't need to remember which goes into which, it ain't gonna dissolve your shorts and privates, it ain't gonna take ten minutes (perhaps ten seconds), and you won't need rubber gloves.
IF the copper metal surface is too rough then you will need to resort to polishing.
Reply to
Don Wilkins
Just to make sure my advice wasn't the blathering of someone that had not actually done it, I used some 1200 grit sandpaper on a small piece of copper and followed that with some brasso on a paper towel. The results were a finish that you can see yourself in. Dan
Reply to
Dan Caster
I'm surprised at this since, IIRC, copper chloride is insoluble isn't it? Would you please explain why this works?
Ted
Reply to
Ted Edwards
Cupurous or cupuric? ;) (I believe there's a difference)
Tim
-- In the immortal words of Ned Flanders: "No foot longs!" Website @
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Reply to
Tim Williams
Copper(II) chloride is considered water soluble.
Copper(I) chloride is not very soluble in water but is quite soluble in muriatic acid.
It forms a chloride complex. This is also true of AgCl which is much less soluble in water.
Reply to
Don Wilkins
Thanks.
Ted
Reply to
Ted Edwards
I didn't know where to find HCL so I used some buffing compound with mild abrasive, and it took it off. I didn't have a motorized buffer; instead I used a drill adaptor and a cotton wheel. Took about an hour, but worked out fine :)
Reply to
Prune
The Surplus Center has an adapter that goes on a motor shaft and has threads that will hold that cotton wheel. They also sell motors, but you might be able to find a motor locally and save on freight. A 1/3 hp motor will be adequate for occasional buffing. It sounds as if you may be wanting to do some more polishing in six months or so.
Dan
Reply to
Dan Caster
HCL = pure version of Muriacid pool acid - found in pool supply houses, garden shops that have pools supplies - e.g. K-Mart etc.
Reply to
Eastburn

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