Copper sulfate is a chemical compound that produces stunning blue crystals. Plus, it’s really easy to grow them. In fact, it’s one of the easiest compounds to grow crystals with.
There are already many guides on growing copper sulfate online. But most of them do not have detailed procedures. Plus, the crystals that they show are usually imperfect.
Therefore, I’ve decided to share my own procedure on growing copper sulfate crystals. It is based on my experience over the past 3 years. And they have given me great results.
Let’s get started.
Growing copper sulfate crystals
To grow copper sulfate crystals, you’ll need:
- Copper sulfate powder
- Very hot water
- Two large jars
- A flat dish
- A spoon
- A filter funnel
- A thin nylon fishing line
- An electronic balance
Copper sulfate is frequently used to demonstrate crystallization in high school labs. Like all copper compounds, it is mildly toxic. It’s best to handle copper sulfate with gloves, although touching them occasionally is fine, provided you wash your hands afterwards.
But if you want to grow crystals with small children, copper sulfate is not a good idea. They might accidentally eat it, and things can turn nasty. Consider growing other non-toxic crystals such as octahedral alum crystals or star shaped MAP clusters (a type of fertilizer).
Now, let’s decide what type of copper sulfate crystal you want to grow.
Types of copper sulfate crystals
There are 2 types of copper sulfate crystals you can grow: single crystals and crystal clusters.
The procedure to grow them is slightly different. Big single crystals like to grow from exactly saturated solutions which are more stable while crystal clusters grow from less stable, supersaturated solutions.
What is the difference between a saturated solution and a supersaturated solution?
A saturated copper sulfate solution at room temperature is a solution that has the maximum amount of copper sulfate dissolved in it.
At room temperature, 100 ml of water can dissolve around 50 grams of copper sulfate (pentahydrate).
However, hot water can dissolve more copper sulfate than cold water. So if you dissolve a lot in hot water and then let the solution cool, it is now supersaturated because it contains more copper sulfate dissolved in it than what should have been possible at room temperature.
In this tutorial, we will be focusing on growing big single crystals from a saturated solution. Single crystals are harder to grow, but they are also much more satisfying. Click here if you want to learn how to grow a crystal cluster instead. That guide also covers some FAQ in detail.
This tutorial will be divided into 5 parts:
- Part A: Getting the copper sulfate
- Part B: Preparing the solution
- Part C: Growing the seed crystal
- Part D: Growing the main crystal
- Part E: Drying and storing the crystal
Part A: Getting the copper sulfate
Copper sulfate is a chemical that’s commonly used as a fungicide, rootkiller and drying agent. You might find it in powder/crystalline form at Home Depot or your local gardening store. Alternatively, it is cheap and easy to find online.
The copper sulfate from some sources are purer than others. Try to find ones that look a deep, stunning blue rather than pale or turquoise.
Part B: Preparing the solution
- Dissolve 50-55 g of copper sulfate powder for every 100 ml of very hot, but not boiling water.
- When all the powder has dissolved, your solution should be a clear blue with a slight tinge of purple. If it looks cloudy, it might contain impurities. You can either choose to proceed (results might not be that good), or purify the solution first.
Left: Impure copper sulfate solution; Right: Pure solutionCopper sulfate crystals grown from impure (left) and pure (right) solutions.
- Wait for your solution to cool to room temperature.
- Filter it using (tissue paper/coffee filter/filter papers) if necessary.
- Pour the filtered solution into a jar.
- Sprinkle a few grains of copper sulfate powder inside it.
- Leave the jar to sit overnight.
It is difficult to make an exactly saturated solution of copper sulfate. Therefore, in the previous steps, you prepared a slightly supersaturated solution.
By sprinkling some powder into the solution, these grains act as sites to allow crystals to grow, hence “absorbing” the excess copper sulfate in the solution. Missing this step is why most crystals you see online are badly formed.
After 1 day, most of the excess copper sulfate should have been absorbed, and you should have a bunch of crude crystals at the bottom of the jar.
Pour about 50 ml of the solution into a flat dish. I used a petri dish, but you can use any dish you like, as long as it’s not made of metal.
Pour the remaining solution into a new jar, but leave the crude crystals behind in the old jar. You can re-dissolve them for future projects if you want.
Part C: Growing the seed crystal
Place your dish in an undisturbed location like a cupboard or a shelf in the storeroom. After a day or two, small beautiful crystals will have formed in it.
Using tweezers, gently remove the most perfect crystal you can find. This step is very important, because the crystal you choose will be the one that you’ll end up with.
Be careful not to scratch it. Then, tie one end of a fishing line to a stick/pencil, and the crystal to the other end. It might be a bit difficult, so try to choose a crystal that’s slightly bigger to ease tying.
After that, just suspend the crystal in your new jar of growing solution that you prepared earlier.
Consider tying a few more crystals and letting them grow at the same time. This way, if you accidentally mess up one, there’s still a few around. Regardless, all you have to do now is to leave the jar at an undisturbed location and wait.
Part D: Growing the main crystal
As time passes, the crystals will slowly grow in size. But there’s a golden rule that you need to follow:
The slower crystals grow, the more beautiful they will turn out in the end.
This is because as the solution slowly evaporates, the excess crystal particles arrange themselves in an orderly manner to produce a perfect single crystal. If you let the solution evaporate quickly (like in the sun) or expose it to big temperature changes, this process is disrupted. The arrangement of particles becomes disorderly, and thus, your crystal might become jagged or deformed.
So be patient. Try not to lift them out of the solution. If you want to check on their progress, shine at it with a flashlight.
Also, cover the lid of the jar halfway to slow down evaporation (but not completely stop it). After a week, the crystals should be much bigger:
After some time, you might also notice that many smaller crystals have started forming at the bottom of the jar. You don’t want this; they compete with the bigger crystals, hence slowing down the growing process.
But don’t try to remove these crystals one by one. Just remove your main crystals, put them aside, decant the solution into a new jar and then place them back inside. This whole process should take less than 1 minute to minimize interruption to their growth.
Place the crystals aside, while you transfer the solution to a clean jar. This process should take less than 1 minute. These leftover crystals at the bottom of the jar do not need to be discarded. Keep them, or recycle for future use.
After about 2 weeks, you should consider separating your crystals. Put each one in an individual container to grow. This way, they will grow faster because they don’t have to compete with each other.
Given enough solution and a sufficiently big container, you can grow them as large as you like. After 1 month, I decided that mine was big enough and removed it from solution.
Dry the crystal using a paper towel or filter papers. You don’t really need to wipe it, just place it on top of the paper and it’ll soak up the solution. Remember, never wash the copper sulfate crystal, or it’ll re-dissolve. Even a quick rinse will cause the edges to become less sharp.
After that, you’re done! Take it out for some pictures or show it off to your friends.
Part E: Storing the crystal
Copper sulfate crystals are bright blue because they contain water molecules inside their crystal structure. If left in the open, they might dehydrate, turning white.
Dehydrated crystals that have lost their sleek, shiny surface. Left alone, they become whiter and the surface flakes off.
To prevent this, you have two options:
- Coat it with a layer of nail polish. The nail polish protects the surface, preventing dehydration.
- Put it in a ziplock bag, then store it in a sealed container together with a little copper sulfate powder. The powder maintains a stable condition inside the container, preventing dehydration.
There you go. The best way to grow single crystals of copper sulfate.
In fact, copper sulfate crystals were the first ones I grew back in my high school chemistry class, and they were what introduced me to this hobby, which I’ve fallen in love with ever since.
I hope you enjoyed the read. If you have any questions, feel free to drop a comment below. I have also compiled a list of frequently asked questions such as:
- How do I grow a crystal cluster instead of a single crystal?
- Will the string get stuck inside the crystal?
- Can I grow copper sulfate crystals on objects like bones?
- Why are there flaws in my crystal?
You can find the answers to all that here.
Or you can also check out how to grow stunning crystal clusters from fertilizer.