subject: Best Methods For Cleaning Bronze Coins [print this page] If you are a collector of bronze coins that are full of patina, verdigris, dirt and other unsightly residuals time has caused, you may want to clean them to see what lies underneath all of that grit. There are several ways you can go about cleaning them, but of course, always be careful whenever you attempt a new cleaning method on anything that is hundreds or thousands of years old.
Many people find that they have success when they use a toothpick and a soft eraser for the coating, especially if it is sandy or greasy. You can also use brushes, but begin with a soft one and advance to courser bristles if warranted. There are also many people who swear by the use of carpenters glue, which seems to work extremely well for the dirt and false patina that plagues a big majority of bronze coins. If you head to your local drugstore, ask a clerk for something called Vitrinol copper soap to clean up your pieces. Using a moist cloth, you apply this soap and rub the coin to remove dirt and patina.
One of the most popular substances used for cleaning bronze coins as well as those that are made of copper is good old hydrogen peroxide, which fortunately is also extremely inexpensive and can be found just about everywhere drug stores, grocery stores, and even gas stations and convenience stores. Immerse your bronze coins into a hydrogen peroxide bath, but not for too long. This will loosen and remove quite a bit of dirt from them.
If you have pieces that have undergone changes to change the color to a dull orange or red, or even a coating of black, the bronze coins have copper scale that is caused by annealing of the pieces. Unfortunately, this often destroys at least the coins surface, and sometimes the entire piece will be ruined. However, you can attempt to remove this scale by putting the coin in dilute sulfuric acid for no more than ten minutes. Rinse the pieces with water under the faucet and rub vigorously afterwards with a copper cleaner or a copper cleaning soap. Afterwards, you can dip them in very diluted sodium hydroxide (use caution: it is caustic) and then rinse.
Have you tried boiling your bronze coins for ten minutes in water with some common baking soda added to it? This might be all you need to do the trick. You can also immerse your pieces into a solution bath of 10% ammonia for a few minutes then soaked with several changes of water followed by rubbings by a brush. Be careful with this though, because the bronze coins might be damaged if they are exposed to the air for too long while you transfer them from the ammonia bath to any acid bath, and immerse them briefly in a 5% hydrochloric acid solution for neutralization.
