Electroplating

I checked our copper-aluminum battery 2 weeks later and it was producing a solid 2.7 V. We took it apart to check on everything.  The vinegar electrolyte solution was now a deep blue from the copper dissolved in it.  I poured it into an empty spaghetti sauce jar. 

 

The copper tubes had green crystals at the top where they were exposed to the air.  The aluminum bars were coated in copper.  

This gave me an idea.  I grabbed a fork, put it in the jar, with a copper tube on the other side, and hooked it up to a 9 V battery, (copper +, fork -).  I sharpened two ends of a pencil and connected it into the circuit as a resistor so the battery wouldn't short too fast.  (Graphite conducts electricity and acts like a resistor.) 

Above you can see the oxygen and hydrogen gas bubbles coming off the metal electrodes (because of water electrolysis).  Too much current was going through so I used a longer pencil section in the circuit. 

I added some more water to increase the volume of metal exposed. 

Above is an image of the fork and the copper electrode after the treatment.  The fork had a lot of black residue that washed right off.  Below is a picture of the copper that remained after a good scrubbing. 

In retrospect, perhaps it is not a good idea to try to electroplate stainless steel.  I tried hooking up several coins to plate with copper.

We plated several coins.  I hooked up the positive and negative backwards with the nickel and the end of the alligator clip dissolved away (see below).  We made a copper dime, nickel, and two copper quarters.