The Amateur Chemist

How to make gold and silver pennies


I will present here two methods for making both silver and gold pennies. The first method utilizes the zinc sulfate, while the other uses a combination of zinc oxide and sodium hydoxide. 

 

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Method 1

First, dissolve 30 grams of zinc sulfate and into 100 ml of water. You can also use zinc chloride if you don't have any of the sulfate. Then drop in several pieces of zinc metal into the solution. Finally, heat the solution up to boiling and drop some copper pennies into the solution. They must be touching the zinc, for the reaction to work. 

Heat the solution for several minutes for the reaction to take place. Wait until the pennies turn silver on both sides. Then take them out quickly and dunk them is some cold water. Alternately, for better results, get a large amount of water (5 gallon bucket) and dump it in there in one move.

To make the silver pennies gold, simply take the silver ones out of the water, dry them off, and put them on a hot plate. The hot plate needs to be around 300*C. It should turn fully gold within several tens of seconds. Then dunk it, again, in some cold water.


Method 2

The next method uses zinc oxide and sodium hydroxide. First make a solution of sodium hydroxide by dissolving around 2 grams in about 10 ml of water.  I usually scale this up a bit. Then, put a spatula full of zinc oxide into this solution. It will initially form a white suspension, that will eventually dissipate to allow a see through solution. If it doesn't, you can add a small amount of sodium hydroxide again and stir until the suspension disappears. The solution will become quite hot from the sodium hydroxide going into solution.

Then, simply put some strips of zinc in the bottom like the last method and put your pennies on top. Wait for them to turn silver, and do the same steps as the last method for washing and turning it into gold brass.


Explanation

There are several explanations for how this works, and it is not really known how it fully works. One explanation is that the zinc sort of diffuses into the copper in the first step to form a type of white/silver brass. Then when you heat this brass up, it decomposes into gold brass, the normal kind.

Another explanation is that you are simply plating the zinc on top of the copper, and when you heat the penny, the zinc diffuses into the copper forming the gold brass.  Either way, it looks pretty cool. The silver and gold layer will only last for a certain amount of time before it wears out.

The pennies must also be as clean as you can possibly get them!!!  The cleaner they are, the better this experiment will work. Also, the shinier they are when you start, the better they will turn out.  A great way to clean pennies fast is to get some vinegar and dissolve some sodium chloride (table salt) in it. Then, simply put the pennies in the solution for a while, and try to polish it with your finger. It should become quite shiny very fast.