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.
Some fantastic info here Chase, really appreciate the effort you’ve put into sharing it with us. One tip that has worked well for me that you might like to try…
I’m lacking dexterity (and patience !) so rather than hopelessly fiddling with trying to tie a tiny seed crystal onto my fishing line, I’ve found that a microscopic dot of cyanoacrylate glue (superglue / crazy glue) on the very tip of the line is a quick, simple and very effective way of attaching the crystal, and when you’re done a gentle tug will usually remove the line without a trace. Also tried the same technique with a long hair which worked well, though that’s getting back into ‘fiddly’ territory again !
It doesn’t seem to affect crystal growth at all, though have only tried it with CuSO4 so far… planning to try some of the other materials on your site when time and space allow.
Great. That’s a tip everyone can use. Thanks for sharing!
This is by far the best practical guide I have come across in my quest to grow Copper Sulfate crystals. I wish I had come across it before. I grew a magnificent poly crystal but am going back to try for a third time to get a single chonky (yes I said chonky lol) crystal. Apparently my solution was mega saturated. I also disintegrated or redissolved several of my fine seed xtals by not letting the solution cool enough first. That hurt but lesson learned haha. Thank you, Chase, for you information and enthusiasm. I wish you the best in crystal growing, academia, and life.
Thanks. Good luck for your chonky crystal, and may your path lead you wherever you want to go. Have a good one!
Thanks so much
I just bought the copper sulphate today and was wondering how to do it.
Do you have any tips for table salt crystals because mine always end up small and ugly
Table salt crystals grow the best when they are undisturbed. Try preparing a saturated salt solution, add a bit (2-3%) of distilled water to dilute it, and then leave it in the storeroom/basement. Sometimes my best crystals form when I start growing them, forget about them for a few months, and come back to see amazing crystals.
You can also check out my guide on how to grow table salt crystals: https://crystalverse.com/sodium-chloride-crystals/
Hello, thank you for taking the time to produce this detailed information. Once the crystals are formed are they then safe to touch?
Copper sulfate crystals are mildly toxic. You can touch them, but be sure to wash your hands afterwards. If you coat them with a layer of nail polish, then they are safe to touch.
Hey chase I was just wondering.In one of the steps you said filter is necessary how do I know if it’s necessary to filter it?
Actually you don’t need to filter the solution ~ it’s just that filtering it will make it easier to grow good crystals. I always filter my solutions unless they look perfectly clear from the start.
Hey Chase, how many crystals should be growing on the bottom of my Petri dish? In your pic it looks like they’re just a few, but I have a lot more, almost like a sheet. Don’t get me wrong there’s some good seeds in there but is my mixture evaporating too quickly?
It’s more likely that your solution was slightly too saturated. This is a very common problem. Next time, if you face the same problem, add a few drops of plain water into the solution to dilute it. After that, fewer crystals will form.
As long as it doesn’t prevent you from getting good seeds for tying, you don’t need to worry about it.
Hello! Thank you for the guide!
I was wondering: When you grow the seed crystals on a Petri dish, do you suggest closing the Petri dish with a lid, to isolate dust, etc.? Or would this make evaporation too slow?
On hotter and drier days, I use a lid, while on cooler days I remove the lid. It all depends on your surroundings. If you find that the crystals grow too fast, then use a lid.
Hi, I’m going to try this soon for the first time. I have a question. When you start growing the crystal the nylon thread grows into the crystal, not? Won’t this be ugly in the result?
Yes, the thread grows into the crystal. But since the nylon thread is very thin, it is almost invisible, especially if you cut it away after you are done with growing it.
Thank you, bro. Sorry, no speak English..(
I am very grateful to you for this information in your site.
It’s okay. Good luck!
Fucking awesome, dude!
Thank you, this is great! I tried this in school once, and loved the results. Then I tried something else- and you might find this interesting. So I took Copper Nitrate and reduced it with KOH, which gave a green solution (we speculated it had malachite in it). We tried to crystallize from that solution, but it gave the powdery, sandy residue you mention at the top of your article. Maybe something to try, if you can develop it into a crystal? Would love to hear insights.
Hello. Mixing copper nitrate and potassium hydroxide forms copper hydroxide, which is a blue-green powder. Unlike the residue I mentioned, copper hydroxide is insoluble in water, which means it’s not possible to grow crystals with it in the conventional sense.
Someone on Reddit did manage to make some malachite. He also included his procedure. It’s more like a crust than a shiny crystal, but still impressive imo.
Thanks for a great tutorial.
I have a 10mm crystal that is very nice, can that be grown bigger by adding it into a jar of solution & leaving it.
Yay! Of course, you can keep growing the crystal by putting it in more solution. However, make sure the solution is exactly saturated (an undersaturated solution will cause the crystal to dissolve, a supersaturated solution will cause the crystal to grow quickly and look ugly). To prevent this, prepare a supersaturated solution, sprinkle some crystal seeds inside and wait for several days before decanting the solution and using it to grow your main crystal. Good luck!
Hi! Great guide. I was curious about how I should dispose of any extra solution. Is there a way to separate the still dissolved copper like waiting for most of the water to evaporate or some other way to deal with it?
Hey there. The easiest way is to let all the water evaporate, then you’ll be left with some copper sulfate crystals that can be stored in a small container, ready for use in the future.
If you want to really throw everything away, either contact a waste disposal service, or convert the copper sulfate solution into a form that is less toxic to the environment. The waste disposal service can be expensive, so here’s how you convert the solution. Drop a bunch of iron metal into the copper sulfate solution, and wait a week or two until the solution turns completely green. This is due to a metal displacement reaction in which copper sulfate reacts with iron to form iron sulfate, while copper metal precipitates out. This iron sulfate solution can then be disposed of.
Awesome content! I will definitely follow your work! I was wondering if it’s safe do laser print something in it, like someone’s name so I could gift it to them!
Thank you! Safety side, I think it should be fine. But you might want to try it out on a small crystal first because I’m not entirely sure it will work.
This guide is very helpful. Is there any way to change the colour of the crystal without affecting its growth or shape?
Thanks! No, it’s not possible. Of course, you could look for another compound that has a similar shape but a different color. Manganese (II) sulfate crystals, for example, look similar to copper sulfate crystals but are a light pink.
Do you mix up more solution following the same recipe to make up for the evaporation when trying to grow the big crystals? Or mix up enough to last a month or 2 in the beginning?
It’s better to do a small trial run first. Once I’m sure of the purity of the copper sulfate, then I’ll mix up enough to last a month or 2 in one shot, and store the excess in a big jar.
Is it at all possible to use an already naturally formed crystal to grow more like that crystal? Maybe like an amethyst or plain quartz crystal?
Also just out of curiosity, do gems work in these growing processes?
Most naturally formed crystals, like quartz, form under very high heat and pressure deep in the Earth. While it is technically possible to grow a piece of these crystals, you would need similar conditions to achieve such an effect.
In fact, pure quartz crystals are grown for industrial applications. Rubies and diamonds can also be created in the lab. But unless you have specialized equipment, it would be nearly impossible to grow these “gemstones” at home for the average person.
I’ve recrystalized my copper sulfate following your guide, and realized that my starting material is about 50% anhydrous CuSO4, which meant I added more CuSO4 at the 50g to 100ml ratio. Because of this, I ended up with some rather sizeable crystal clusters that have up to 1 inch crystals in them. To use these crystals for the growing solution, should I grind them up in a mortar & pestle (granite) first, or will they dissolve reasonably fast enough in fresh distilled water?
Also, when you say to “wash” the crystals, are they just being washed with clean water? Won’t that just re-dissolve the crystals?
Nice. The grinding is optional. Just heat the solution for about 15 minutes and the chunks will dissolve. Of course, powder will dissolve in less than 5 minutes, so that’s up to you.
I recommended washing the crystals quickly with cold water. Cold water dissolves the crystals much more slowly, so any loss is negligible. Much more convenient than using an organic solvent.
I love the fact that your directions are so detailed, and they’ve been very helpful. The problem that I’m experiencing is that I have a hard time growing the little crystals in order to grow them into larger ones.
I follow the directions but end up with a layer of crystalized powder at the bottom of the dish, but no crystals.
What am I doing wrong?
It might be because you rate of evaporation is too fast, or maybe you accidentally scratched the little crystals when you handled them. Try pouring the solution carefully into another container, cover it partly with a lid, and then leave it in an undisturbed area. That should help. Good luck.
Awesome crystals and informative instructions. What happens to the fishing line after the growing process is over? Is it embedded within the crystal or can it be removed?
Thank you. Unfortunately, it is stuck inside the crystal, though barely noticeable. Alternatively, you can grow the crystal at the bottom of the container. In that case, no fishing line will be needed.