Sure. A couple of the quickest ways to thoroughly tarnish a coin would be: Let an egg get rotten, then put your coin in a small glass dish and break the egg over it. Lots of hydorgen sulfide, which will blacken the coin nicely in short order. Crush a bunch of kitchen match heads, make a paste and apply it liberally to both sides of the coin, then bake for 30 minutes at 450 degrees F. Of course, both methods will work best on silver, but should seriously darken copper/bronze, brass, and cu-ni; and corrode aluminum or zinc. Seriously, why on earth would you want to do that? Even the folks who call tarnish "tone" generally agree that artificial toning ("AT") is bad.
Chop up a rubber band, and sprinkle the pieces over any silver. Keep a close watch on the coin as it will tone very, very quickly and turn black if you leave it too long. Make sure to rinse the coin with distilled water after removing it.
I was a little surprised to see so many folks who opinions I've learned to respect provide information on how to become a toning doctor, but OK, here's some more ways to ruin your coins. - Using a standard toaster oven, place your coins on the center of the tray and toast 'em for about 5-6 min. You can also alternately stack dimes, quarters and nickels and cook 'em longer. Be careful when removing the coins, a coin heated to several hundred degrees will take the skin right of your fingers and simply ruin the coloring you've work so hard to acquire. The colors will amaze you and then you too can sell them on ebay to some smuck who doesn't know any better. - Suspend a coin in a jar with apple, orange or tomato juice in the bottom, but not touching the coin. Seal the jar and place where it receives sunlight all day long. Check daily and remove the coin when the colors you desire appear, but remember, black is a color to. - Experiment with placing coins on your dashboard where they can be in direct sunlight for several days. - I understand cooking a coin in your oven filled with argon will bring about some remarkable dark blues,.... IF the oven doesn't explode on you. Other gases result in different colors, but all are volatile. There are more methods, but some of them are down right dangerous.
