Growing Copper Crystals Using Electroplating

I tried growing copper metal crystals by Electroplating/Electrowinning after I saw this blog post by Science with Screens. In his experiment, he used a constant voltage source. However, when using a constant voltage during electroplating and without any continual mixing of solution, the copper (II) ions near the anode will become depleted and the resistance of the solution will increase, resulting in a decrease of current.

Here I used a constant current circuit to keep the current constant during the entire process.

• Electrical wires.
• Battery (9V or 12V) or a power supply.
• Scrap copper (I used copper from electrical wires).
• Heat shrink tube / electric tape / Hot glue gun for insulating the exposed electrical connections.
• Constant current circuit (Sink or Source).

For the constant current circuit, I used an LM358 op-amp, 2N3904 NPN transistor, TL431, 10K potentiometer and some resistors (3.3k, 1k and 47 ohms). The TL431 provides a 2.5V reference. The 47 ohm current sense resistor allows us to set the current from under 1mA to around 50mA. At higher current (<40mA), the sense resistor and transistor started overheating.

Any other constant current circuit works fine (LM317, Linear, switching...), just replace the load with the copper cell.

I dissolved around 60g of copper sulfate CuSO4 in 1L of water and transferred them to a jar. I soldered the scrap copper to an electric wire (The anode) then covered the solder joint with some hot glue to prevent any unwanted corrosion of the electrical connection. Then I soldered a small piece of solid core copper wire to another wire (The cathode) and removed the insulation for around 1cm of the tip of the wire.

I connected the anode to the positive side of the constant current circuit and the cathode to the negative side of the constant current circuit.

Using a multimeter I set the current to around 12mA.

Because at the anode copper ions are produced and at the cathode they are being consumed, the solution starts to develop a gradient where, near the cathode, the blue color becomes less intense and near the anode, the blue color becomes more intense. So every few days I gently stir the solution to remix the layers.

Due to the low current, it took 36 days to grow this crystal. The lower the current the larger the crystals formed. However, I noticed in another experiment that if the current is too low (less than 5mA), the crystals never formed because the voltage at the cell was too low for the redox reaction to take place.

As soon as I was satisfied with the crystal I stopped the experiment and was greeted with a very beautiful copper crystal. It will tarnish a bit when exposed to air but you can restore its shininess by dipping it in some vinegar.

This was my first instructable. Enjoy!