Poor Dead Penny

With luck, you are following up on my previous post about penny sorting. If not, you may want to check it out.

So I ended with suggesting there is a fun way to dispose of the new, copper-plated zinc pennies. Sure, we were all taught as children that mutilating money is wrong. But the point of that is to not damage money that will be circulated. There is no law against permanently taking money out of circulation; that is just a permanent loan to the treasury.

So my playful and don’t-try-this-at-home method of eliminating plated pennies is fun with chemistry. You see,  zinc reacts energetically with muriatic acid (HCl), the stuff you buy by the gallon to etch concrete or stabilize the pH of your pool. But copper is effectively untouched by this synthetic form of stomach acid.

So if you scratch through the copper plating on the edge of the new pennies, and drop them in the acid, the result is fizzing hydrogen gas (danger) mixed with a vapor of the strongest common acid (danger) and eventually leaves behind a depleted solution of acid with zinc chloride and little perfect penny foils. When the reaction is done,  carefully decant and rinse the foils. Make sure you store or properly neutralize and discard the remaining acid.

Ready to Start the etch

For a hollow penny just scratch a hole in the side. This may take a while to etch, as the hydrogen bubbles have to get out for the acid to do its work. I like to grind away the whole edge to make separate delicate head and tail foils. This etch still takes a few hours.

So the Object at Hand is this set of penny foils, showing odd points of view of our most diminutive denomination of cash.

The inside of a penny, looking up

HCl ate the brown oxide, leaving a foil too thin to hold its shape in this 1982 zinc penny

This penny plating was so thin that the acid let the light through where the die cut deepest

1 Response to “Poor Dead Penny”

  1. 1 Dan Klarmann May 2, 2011 at 10:40 am

    The camera? Well, I took a time lapse of the etch. But it was very out of focus. Maybe I’ll do it another time and make sure I set the camera to macro mode.

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