To Restore a Coin to Mint Condition with Chemical Treatment (Benzotriazole), you have to put on gloves to avoid direct contact with benzotriazole (BTA). After that, Dissolve one to three percent concentrated BTA in ethanol or water. Then, Drop the dimes, nickels and quarters in the solution. Next, leave the objects in the solution under a vacuum for one day or more. Forth, Remove the objects from the solution and wipe off the coins with using a rag dipped in ethanol.