Toning Copper Pennies

If people "got mad" at you for asking how to clean and re-tone coins, that's because coin cleaning and artificial toning are two of the most controversial topics in coin collecting. The main reason being that coins that are cleaned and/or artificially re-toned are sold by a few unscrupulous dealers to unwary buyers for far more than the coins are actually worth. As far as coin collectors are concerned, the message is, "Don't clean your coins!!!". But in the name of Science, I'm prepared to risk the ire of my fellow collectors and offer a few tips.

You can't actually do anything to a coin to genuinely make it "look like new" - apart from sending it back to the Mint and having them melt it down and make you a new coin out of it. [:0] You can use mild or dilute acid (for coppers, lemon juice and vinegar are commonly suggested) or some other technique to remove surface oxidation and re-expose the bare metal, but you can never restore the shininess that the coin obtained when being struck at high pressure. Any such treatment actually damages the coin's surface and lowers it's value to a collector.

As far as re-toning is concerned, a nice hot oven (300°F or 150°C) is a good start, but a more realistic effect might be obtained if you cover the coin, particularly with something containing a little sulfur, before baking. A piece of paper, cooking oil, motor oil, diluted shampoo - do a little trial and error.

Note: as I'm a collector, I haven't actually tried any of these ideas myself, and they probably won't work so well with modern (post 1982) US "copper" cents, as they're not really made of bronze, but plated zinc. Same goes for British pennies, Euro cents or anything else that looks "coppery" - the price of copper has risen too high for countries to be able to afford solid bronze coins anymore.

Hi Kendra

I dont think you will get in trouble here for your question.

copper is a very reactive metal, to clean the coin try a very quick dip in something like tarnx, 1 second and directly under running water, then a mild detergent like dish soap to remove all of the acid.

since copper is highly reactive to heat and humidity , I'm not sure how long you have to retone the coin to an old appeance? but just carry it in you hand,your pocket, touch it on the surfaces with your fingers, lay it around outside on a picnic table you should be able to darken the coin within a few weeks,in other words accelerate the normal circulation cycle of a cent.

PS the wax that you used on the coin will protect the surfaces from retoning !!!

Rick

Best method I have found in 25 years of specializing in Lincoln cents is to use a washed but used shop cloth from a mechanic...just go to a garage and ask for a couple that have come back from the laundry - most garages participate in a shop cloth recycle type program where a bag of dirty cloths are exchanged for a bag of cleaned ones. Rub the coin in the cloth, holding it up to a light bulb on occasion to heat it up. It will turn brown, nearly hiding any evidence of the cleaning. It's basically a way of speeding up the process of having a hundred thousand people handle the coin over a period of a year or two. The latent oil in the cloth nearly mirrors finger grease to a tee.

Good luck Kendra9 with your school project. Cleaning copper is easy, there are so many products that will clean copper pots and pans etc.

But getting them to tone up again (which normally takes years)in four weeks is something you won't find easy.

Just to let you know, IF you were a coin collector, you would not do any of this to a coin. It de-values the coin. Some pennies are worth hundreds of dollars to collectors. If you ever tried to sell the coin, people who buy coins would know that the coin was tampered with and would consider it ruined. It would only be worth one cent.

It's obvious your teacher is NOT a coin collector. But is using a cheap form of copper, a penny, for your experiment.

The old penny (1909 to 1981) are 95% copper and I'd guess you'd have better luck with one of them. (just make sure it is not a rare date)

The newer penny (1983 to today) are only 2.5% copper. But that is the outer coat of pure copper over a zinc core.

Tell us in four weeks time what method you used, if it worked, and what grade you got for it.

Hummm. I don't know but.....have you thought of starting again?
This time with two pennies, show the teacher the one you cleaned and then 4 weeks later show her the other toned one. [:0]

PS Very important, make sure the two pennies are the SAME DATE. LOL LOL

(this is a joke, you really shouldn't cheat like that on a science project)[:p]

anyone know what happened to it,and can I change it back.

Can't be sure, some chemicals in the wax must have reacted with themselves or with copper.
It's most probably not real silver (unless alchemy is real:) and my guess is that the color will not remain like that.

Kendra, If all else fails, or you wan't to try something else, get a small tupperware-type container. Pour 1/4" or so of high acid content vinegar into the container. Place a small object in the vinegar to lay a penny on to keep it out of the vinegar. Put the penny on the object and carefully close the container. Store the container in a warm place and occasionally check on the penny and turn it over. If I'm not mistaken, vinegar has a high sulfur content. Apple cider vinegar may work better than white vinegar. Maybe someone else knows what kind of vinegar, or of another more/less corrosive liquid like ammonia? I think outboard motor lower-unit grease has an unbelievably high sulfur content. If you live near a marine sales or service center you might want to stop in and ask for a small amount of used lower unit grease. I appologize if any of this ends up being a waste of time. At least it will help with documenting your experiment. Please let us know how your project turns out.