The Extended Guide to Growing Copper Sulfate Crystals

a large copper sulfate crystal

How to grow clusters of copper sulfate crystals? Will the string get stuck inside the crystal? Can I grow them on rocks and bones?

This article is a companion to my main guide The Best Way to Grow Big Copper Sulfate Crystals. If you haven’t seen it, I suggest you check that one out first.

Having grown them for 3 years, I’ll cover the following to the best of my knowledge:

  • How to grow clusters of copper sulfate crystals?
  • Will the string get stuck inside the crystal?
  • Can I grow the crystals on rocks and bones?
  • General tips and troubleshooting
    • Flaws
    • Crystal creep
    • Crystals growing on the string
    • String breaking
    • Handling
    • Storage

How to grow clusters of copper sulfate crystals

In my main article, I provided a detailed procedure to grow individual crystals. If you want to grow clusters instead, you just need to tweak the steps a little:

Dissolve 70g copper sulfate per 100 ml water (instead of 55g to grow single crystals). To achieve this, your water must be very hot. If not all of the powder manages to dissolve, you can reheat the solution, but be sure not to boil it. This is because boiling causes the compound to decompose.

It takes some time to dissolve 70g in 100ml of water. Heating is often necessary. But you don’t have to use a beaker.

After all the solid has dissolved, filter the solution while it is still hot into a jar. Cover the lid of the jar. Wait for the solution to cool to room temperature.

Tie a seed crystal to a string. Unlike the procedure for growing single crystals, this seed crystal does not have to be perfect. You can choose any chunk you like (the leftover ones at the bottom of the container from the previous article do nicely). Make sure the knot is tight. Lower the seed crystal into solution.

Take note: You are lowering the seed crystal into an extremely supersaturated solution. Therefore, growth starts immediately. Within 5 minutes the crystal will have grown in size.

Within 1 hour it should look like this:

While I did mention that the golden rule to growing high quality crystals is to make sure it grows slowly, we don’t need to worry about that here.

In this case, we are taking advantage of the unstable solution to cause a wild cluster of crystals to form. They might not be sleek, sharp and shiny, but we can fix that later.

Over the course of the day, the crystal will grow quickly. But having sucked up all of the extra dissolved copper sulfate in solution, it should start to slow down by the second day. You can now remove it and call it done! It’s that simple.

But I like to let it stay inside for a week or so. This gives time for the crystal to grow slowly, and since it grows slowly, the outermost coat of the crystal looks smoother and more transparent.

A cluster of copper sulfate crystals growing in a beakerIn the picture above, notice that a layer of crystals have grown at the bottom. They are now competing with the cluster for growth, so it will not be able to grow much bigger. For further growth, transfer the cluster to a new container with fresh solution.

But I thought it was good enough, so I removed it:

A cluster of copper sulfate crystalsTo store it, use the same procedure for single crystals.

Will the string get stuck inside the crystal?

Yes. It is almost invisible if you use a very thin nylon fishing line, but there’s still no way to get it out.

If you don’t like that, there are two workarounds:

  • Grow the crystal directly on the string
  • Grow the crystal at the bottom of the jar

Both are doable, but tricky.

Grow the crystal directly on the string

To apply this method, stick the fishing line into the dish with the seed crystals, and try to make one of them “grow into” the fishing line naturally as the crystal enlarges.

Once the crystal is securely attached to the fishing line, you can then hang it and grow as usual.

When you finish growing, you can pull the fishing line out of the crystal. Sounds good in practice, but based on my experience, it can be quite hard to coax the crystals to grow into the line.

Grow the crystal at the bottom of the jar

This method does not use any strings. Just let the crystals form naturally at the bottom of the container, and let them grow. Make sure the container has a flat bottom.

Growing copper sulfate crystals at the bottom of a beakerIf you just want to grow some crystal clusters, it’s perfectly fine. But if you want to grow perfect single crystals, there is a very high risk that a bunch of small, fine crystals will start forming around your main crystal and start sticking to it.

By growing them at the bottom, there’s a high risk the crystals will stick to each other.

If you think you can push them aside using a stick, or remove interfering crystals using a tweezer, the answer is no. Don’t do it.

If you accidentally scratch the crystal (which happens 99% of the time), you will introduce thousands of microscopic crystal particles into the solution, forming crystal sand at the bottom of the container that sticks to everything, ruining the whole batch.

Thus, growing copper sulfate crystals at the bottom of the container is very difficult indeed. It requires micromanagement, a stable temperature and good evaporation control.

Finally, crystals grown with this method will normally have one side which is badly formed, because of bad solution circulation.

The crystal face indicated is rough and jagged because it was not well exposed to the growing solution.

This problem can be solved if you can find a way to stir the solution continuously (by rotating the container slowly, using a motor connected to a stirrer etc.)

Can I grow copper sulfate crystals on rocks and bones?

Yes! Crystallized objects can be beautiful ornaments. Many people make and sell crystallized insects, skulls and sculptures.

A crystallized cicada and a piece of driftwood respectively, by Cody Booth, a professional craft peddler who has grown these crystals since 2014.

Unfortunately, I haven’t crystallized any objects myself so it is not my area of expertise. However, I am able to address some common issues that beginners face when trying to crystallize objects.

One of these issues is that the crystals refuse to stick to the object, and instead form at the bottom of the container. This usually occurs when the solution used is not supersaturated. Exactly saturated solutions might be good for growing single crystals, but you want that extra supersaturation to allow the crystals to form in clusters on your object.

An effective way to ensure crystals do form on your object is to first dip it in a supersaturated solution, then immediately take it out and let it dry for a few minutes. Hundreds of tiny crystals should have been formed. Then re-submerge your object and they’ll start growing bigger.

Finding the perfect conditions for crystals to form well on any object is an art. It requires lots of patience and experimentation, but the results are stunning.

Copper sulfate crystal sculptureCopper sulfate crystal art gallerySculptures made by Elliot Bastianon, an artist and designer whose work is displayed in a gallery in Australia. Check out more of his work here.

General tips and troubleshooting

Flaws in the crystal

  • If your crystal has defects, it might have been because you weren’t careful enough when handling the seed crystal. Most online guides tell you to let a crystal chunk form overnight at the bottom of the container, break it up and choose a nice piece to use as a seed crystal. This method is very bad and produces inconsistent results; use the one I suggested in this article instead.
  • The defects might also have been caused by growing the crystal too quickly. This leads to inclusions, jagged edges and irregular faces. To fix this, partially cover the top of the growing jar to slow down evaporation.
  • Finally, it might have been caused by big changes in temperature. You can minimize this by growing the crystals in a sheltered environment like the basement. But depending on where you live, such changes might be impossible to avoid, especially during certain times of the year.

Crystal creep

Copper sulfate crystal creepAfter a few weeks of growing, blue crust will start creeping up the sides of the container. Don’t panic, this is completely normal. It appears faster when the surface of the solution is more exposed to evaporation. Some people have suggested coating the walls of the container with a ring of Vaseline. Personally, I just transfer the solution to another cup and continue growing there.

Crystals growing on the string

Don’t use ordinary thread. Use a thin nylon fishing line, and it should solve the problem. Also, don’t keep taking the crystals out for a look. When you do this, droplets of solution might dry on the string exposed to open air, forming small crystals which start growing the moment you put it back in.

String breaking

This should not be an issue for crystals weighing less than 50 grams. If you plan to grow a massive crystal, start off with a thicker fishing line.


It is best to wear gloves when holding the crystals. First, copper sulfate is mildly toxic. Although it’s no problem if you hold a crystal for a photograph and wash your hands afterwards. Second, you might leave fingerprints etched into the crystal. You cannot wash these off, which sucks.


Depending on where you live, the crystals might dehydrate and turn white when left in open air. Put your crystals in a ziplock bag, and place the bag in a container containing some copper sulfate powder. This method has preserved my crystals for 2 years now and they still look absolutely fine.

Some people suggest preserving the crystals in a jar of saturated solution. This method only works if you can ensure that the temperature is 100% constant. Small fluctuations in temperature over time will cause the crystal to keep dissolving and reforming, resulting in rounded edges, and eventually, a shapeless mass.

Parting words

I meant for this article to be a short FAQ, but it has grown rather long. For beginners, don’t be intimidated by all the different factors and problems you need to consider. Just go give it a try, and have fun along the way!

This is the last article in a 3-part series about copper sulfate.

You can find the others here:

If you have any questions, feel free to ask me in the comments. Otherwise, why not take a look at that time I grew crystals out of actual copper metal here.

Happy growing.

Join My Newsletter
Do you love growing crystals? Sign up to stay updated on my latest crystal growing techniques, and learn about awesome new crystals you can grow.
P.S. I'm working on another massive post soon. You wouldn't want to miss it :p

Comments (2)

  1. Matt

    November 18, 2021
    • Chase

      November 18, 2021

Give a Comment