A while ago, local groceries in our town refuses to accept dirty, oxidized coins and said that banks stopped accepting such coins.
This is a burden to us; small retail store owners in remote areas as many of our folks possesses dirty, oxidized or stained coins. If we refuse to accept such coins, it will affect our daily sales. In remote areas such as our place, people buy necessities often with coins, oxidized or stained, and such coins contributes to a large portion of goods exchange such areas.
In places like us, where most people are farmers and farm laborers, those coins are very valuable to them. If we stop accepting those oxidized coins, those poor people might loose several meals.
I am a former jeweler (or at least, my hobby), I know a thing or two how to remove oxidation in jewelries which is also applicable to tarnished or oxidized, blackened coins.
Method 1: Clean by Boiling
You can boil blackened oxidized coins to remove oxides with water and sand. Put about 1/8 inch thick sand (stones and pebbles removed) into the pot or casserole. Pour some water at least 2 inches above the sand. Lay the coins on top of the sand and boil for .10-15 minutes. Remove from heat and flip the coins and boil again for another 10-15 minutes. Use method 2 if you are to clean and old, ancient, antique coin because the sand particle may scratch the coin surface which will degrade its value.
Method 2: Vinegar and Salt
You can soak tarnished coins in Vinegar and Salt Solution. To do this, measure about 1/4 cup of vinegar and add 1 teaspoon salt, mix until dissolved.
Pour the solution into a non-metallic bowl and lay the coins flat into the solution, avoid placing the coins on top of the other. Soak it for 30 minutes to 1 hour. For slightly tarnished coins, 20 minutes is enough. Flip the coins if necessary. After soaking, rinse the coins with clean water. If you are cleaning an old, antique/ancient coin, rinse the coin(s) with distilled water.
