Cleaning native Copper.

Hi there good people,just wondering if you can help with this little problem.I supose it has been asked many times over. I have a lot of Copper laying around both stuff that has gone through the smelter and also large natural specimens of native Copper. Have tried many ways of cleaning this and making it look pretty but to no avail The strongest stuff i tried is the hydrocloric acids this cleans it just beautiful until i take it out then it turns green.I don't really go any stronger then this acid is there something on the market that will take the tarnish and dull copper look off and make it shine? Such a pitty to have these beautiful big specimens sitting here and looking so dull and ugly. Perhaps some of you might know of a simple way to clean these? John

Vinegar and a toothbrush is all I use to clean the native copper pseudomorphs after aragonite from Bolivia. I guess it would work equally well on any native copper. Cleans without leaving an unnaturally bright surface.

Okay Alfredo i shall have a go on the solid chunks and see how it goes but what about the wiry stuff? Any idea there? Some of the ones i have are like a birdnest. Thanks for the tip anyway John.

For "birds nests", use vinegar followed by an ultrasonic cleaner rather than scrubbing with a toothbrush.
Cheers,
Alfredo

John:
Try neutralizing the effects of acids by soaking them in a solution of common baking soda, then scrub/ultrasonic.

If you have the nerve to try something stronger you can try an acid dichromate solution to clean copper. This has been used commercially by various mineral dealers in the past. Take some concentrated sulfuric acid, add about 5% by weight or potassium dichromate or chromic acid and stir till dissolved. This will give a thick dark red/brown solution that will immediately eat up what ever it touches, but it will usually clean copper quite beautifully. This is a very dangerous reagent to use unless you know what you are doing. Use rubber gloves an acid resistant apron, and eye protection. Do not put or pour water into this reagent as it will be converted instantly to steam and blow right back out at you. It will completely eat up a damp paper towel in just a few seconds. The copper is usually very bright and many people think that it is just too bright to look any where near natural. The copper only needs to remain a short time in the reagent and when you take it out you should immediately wash it off in large quantities of cold water. If you want to clean copper half breeds from Michigan I can give you another reagent to clean this material well if you want the silver to be extra bright.
Rock

One of the problems with doing this is you really should properly dispose of this cleaning solution (the chromium is what got a lot of plating concerns into trouble with the EPA).

Hi ,thank you all for the tips but this stuff Rock discribes is a no no as it is just not worth the bother and chances are i would spill some knowing me. I think i leave them as they are or dump them. I just thought there was a safe way,a solution of some sort that would do the trick. After having a talk with my good friend from the Brisbane museum,he strongly advised me not to use the strong accids and reckons it could kill a person if spilled on any part of the body. John

You might not be neutralizing your acid enough after cleaning it. If the hydrocloric is working good for cleaning, just try to neutralize the specimem more after you're done cleaning it.

G'day Mike,you got me going again,you say in your letter (you may not be nutralizing ) What do you mean by this? As it comes out of the hydrocloric acid it is beautiful and shiny,but what happens next is i wash the acid of the specimen with plenty of water. And bingo within a matter of time the beautiful specimen turns dull again and starts to go green.So i thought well i'll fix this problem and sprayed it with hairspray. No good! Somebody said stick it in milk which sounded stupid, but ofcourse i tried. Then vinigar,then something else, but all failed.But it is a challence and am having fun. John

The rule of thumb is that you need to rinse the specimen in clean running water for three times as long as you soaked it in acid. So for each hour of acid bath you're looking at three hours of rinsing in order to make sure you get all the acid off the specimen.

PS: There is a "Mineral Cleaning & Preperation" forum down the menu a bit. People who do a lot of this sort of stuff tend to read that forum and respond to queries - more so than are likely to pick up on a query placed in this forum.

Cheers!

Alan

Hey thanks Alan,you know something? I have never ever looked into this part of the forum and did'nt even know this was there. Now i can see that all the answers are there! How dopey can one get.

John,
I use a 50%/50% water and muriatic acid,
It cleans the copper very brightly. Then I neutralize the acid in baking soda. After they dry, I coat them with clear spray paint. After that they will stay bright for many years.

Ted French

Savages!!! You are ruining good coppers sticking them in acids. Fortunately there are a lot of well crystalized copper specimens that aren't wrecked with acid. Your activities merely make these more valuable. I used to think that Michigan silvers were acid eaten, indistinct blobs; until I got an education at the Seaman Museum. There is little more disappointing than to see a harshly etced copper or silver.

We use a very old method to clean native copper nuggets. All the old collections in Michigan museums were originally cleaned with ketchup. The proccess I use is to put the nuggets in Muriatic acid for ten fifteen minutes to remove any iron, dirt and calcite. then rinse in several pails of clean water and backing soda, so to nuetralize the resido acid. You can air dry them at this point to check them out or you can go to the next step. Take an ice cream pail and empty one or two bottles of any ketchup into the pail. Put the nuggets into the ketchup, making sure they are all covered. Leave them in there for 4,5,6 days. I remove them with a large spoon with the holes in it. Then rinse off the kechup and let them dry off. The copper will look just like the first day they were made. A bright and natural shine. A few may some times oxidize back to a fuzzy green. These will not clean up because of the mix of impurities in the copper. This ketchum method will keep your copper specimens in a like new natural condition for many years. I have some that we cleaned 20 years ago and they still look like they were just cleaned yesterday! If some tarnish and you don't like the look through them back in the ketchup for a few days and they will be back good as new. While the nuggets are in the ketchup, cover the pail so the ketchup doesn't dry out. The ketchup can be reused till it starts turning a brownish black color or you need it for your hambergers. Yuk. The ketchup can be thrown out normally as there is no harmfull or dangerous chemicals used. The muriatic acid can be thrown out following the instructions on the bottle. I like to nutrallize it with baking soda before getting rid of it. Also we don't use vinigar as it can etch the copper. Making a valuable specimen worthless. So enjoy the ketchup cleaning proccess, it works. Dave