Copper metal + Electricity = Copper metal crystals. How cool is that!
I first got the idea of growing copper crystals from a video by the Backyard Scientist.
As I have been interested in rocks and minerals ever since I was a kid, I itched to add it to my collection. But too bad. I didn’t know how to make one.
Fast forward to the present. I’ve learnt about electrolysis in high school chemistry. And that gave me … some ideas. Aha!
It was time to grow my own copper crystals.
I had some copper sulfate salt on hand, as well as scrap metal and a power supply my uncle had given me. It seemed like all I needed.
First, I had to make the electrolyte (basically a conductive bath to grow crystals in). To do so, I dissolved about 15g of copper (II) sulfate in 300 ml of water. The resulting solution became blue.
Next, I poured all of it into a round jar. Then, I coiled some copper plate into the jar, and connected it to the positive terminal. I suspended a second, smaller plate in the middle of the solution as the negative terminal.
Some terms to clarify things:
- Positive electrode aka. anode: This electrode (a coiled copper plate in my case) will dissolve into the solution to form blue copper ions.
- Negative electrode aka. cathode: Copper metal crystals will form on this electrode (the smaller copper plate).
- The copper anode will be sacrificed so that crystals can grow on the copper cathode.
I switched on the power supply and let 0.03A of current run through the solution. After an hour, coral-like branches began to snake down from the cathode. Things were looking well.
Until the entire anode snapped the next day. It had been gradually eaten away until the thing just broke off. Turns out, I had to use a thicker piece of copper.
So I went to the hardware store and bought a 12-inch long copper pipe. The thing wouldn’t fit into the glass jar, so I changed my setup into this:
At last, everything went smoothly. Since this highly informative video suggested that a lower current gives better crystals, I lowered it to 0.01A. It ran for 9 days, and I made a GIF of its growth.
On the 9th day, 4 inches of the copper pipe had dissolved completely. Meanwhile, large shiny crystals had formed in a bunch around the cathode. Looking at the beautiful cluster, I couldn’t resist taking the crystal out any longer, so I stopped its growth. I wish I didn’t. Oh well.
To clean my precious haul, I dipped it into white vinegar, and then some water. This is because when copper metal is exposed to air, it oxidizes and forms a brown oxide layer. Vinegar will dissolve away that layer to reveal the fresh, pink copper underneath.
I took it out into the sun and snapped a few photos.
After that, I stored it in a sealed container.
The good thing about metal crystals is that unlike salt, they do not dissolve in water. So you can wash them as many times as you like.
Copper does oxidize and become dull over time, but that’s easily fixed by a quick vinegar wash.
This was my first successful attempt at growing copper metal crystals, and I was very pleased. Here’s a summary of my process if you want to grow your own:
- Apparatus and materials: 12-inch copper pipe, copper plate, a large plastic container, 30V power supply with crocodile clips and 300 ml of 50 g/L copper (II) sulfate solution
- Dip the 2 electrodes into solution.
- Connect the pipe to the positive electrode and the plate to the negative electrode.
- Switch on the power supply.
- Keep the current constant at 0.01A.
- Wait for 9 days.
- Remove the crystal and wash it gently with vinegar, and then water.
Since I still had 8 inches of copper pipe, I decided to try changing the current to see what kind of crystals I’d get. If you’re interested in seeing a more detailed study of copper metal crystals + very cool pictures, click here for Part 2.
Have some leftover scrap copper? Why not grow stunning black copper acetate crystals.
In the meantime, let me know what you think! Write your thoughts in the comments below.