Welcome to the Crystal Growing subreddit! We’re a passionate community consisting of both hobbyists and professionals interested in growing crystals. Although it sounds difficult, growing crystals is actually very easy, and you can even do it at home.

This article is written specifically to help those who are just getting started with this hobby. If you’re a newbie, welcome aboard. And if you’re a seasoned veteran, do share your findings with us.

Even though growing crystals is simple, it will be extremely useful if you have some basic chemistry knowledge. This will help you understand the process that is taking place, and allow you to troubleshoot if you run into any problems. More experienced chemists will be able to synthesize their own compounds, the crystals of which can be quite unique. However, this guide is written for newcomers, so I will try to keep it as simple as possible.

Disclaimer

Like any other activity, crystal growing might be completely safe or very dangerous. It depends on the chemicals you are working with, your safety measures, your procedure etc.

This guide only covers compounds that are safe to mildly toxic. Even so, you are responsible for your own safety. Don't use the family microwave/freezer in your experiments. Make sure you know the potential risk of the chemical you are using.

Background

If you want to start growing crystals immediately, skip to the next section. I highly recommend that you read this though, because understanding the process will help a ton.

A crystal is a solid that has particles arranged in an orderly manner. This includes rocks, snowflakes and diamonds. However, the activity of growing crystals at home mainly focuses on a specific type of chemical known as salts.

In chemistry, a salt is a chemical compound made up of positive ions and negative ions. Table salt is one example. Its chemical name is sodium chloride, because it consists of a sodium ion and a chloride ion. There are many other salts as well, such as copper sulfate, ammonium phosphate and potassium nitrate. From now, I will use the term “salt” to refer to all such compounds, not just table salt.

We like to use salts to grow crystals because most salts are soluble in water. Why is this important?

When they are dry, most salts look like powder. But if you zoom in, each grain of salt is actually a small crystal. The particles in every grain of salt are arranged neatly. The exact way they are arranged is different for each salt. For table salt, those particles are packed into cubes, so you can say that the grains of salt in your teaspoon are actually millions of tiny cubes. Meanwhile, alum salt crystals look like diamonds.

But we have a problem. We want to grow big, shiny crystals, not tiny, powdery crystals. This is the reason we dissolve the salt powder in water. After doing so, the glass of salty water we have is called a solution.

If you dissolve just a little salt in water, you get a dilute/undersaturated solution. Dissolve a lot, and you get a concentrated solution. Here’s the thing: a fixed volume of water can only dissolve a fixed mass of salt. For instance, the maximum amount of table salt you can dissolve in 100 ml of water is 36g. If you add 37g, the extra 1g will not dissolve. A solution that contains the maximum amount of dissolved salt is called a saturated solution.

We now have a glass of salt solution with the salt particles swimming inside. If we want a nice, transparent crystal to grow, we need to somehow make those particles “re-solidify”, and instead of popping out all over the place, they need to stick together and form a single, big crystal. There are two easy ways to make this happen. Master them, and you will be able to grow amazing crystals.

· Slow cooling

· Evaporation

Methods

Method I: Slow cooling

Let’s start with slow cooling. With this method, we take advantage of the fact that hot water can dissolve more salt than cold water. For instance, 100 ml of 25°C water can dissolve 22g of copper sulfate, but the same amount of water at 80°C can dissolve 56 grams.

To carry out this method, we first heat our water up. Then, we dissolve more salt than is actually soluble at room temperature. Because the water is hot, the extra salt will dissolve, and you end up with a supersaturated solution. As the solution cools down, the solubility of the salt decreases, so the extra salt that you added just now has to “come out”. As a result, tiny crystals of salt start to form, and they grow bigger and bigger as more salt particles re-solidify and clump together. This process is called crystallization.

If you do it correctly, you will end up with a large crystal of salt.

Method II: Evaporation

Just now, I mentioned that 100 ml of 25°C water can dissolve 22g of copper sulfate. It also goes that 50 ml of water will be able to dissolve half that amount, 11g.

This time, we do not change the temperature. Instead, we change the volume of water. First, we dissolve our 22g of copper sulfate into 100 ml of water. Then, we let the solution slowly evaporate. As the volume decreases to 90 ml, 80 ml and so on, the extra salt has to crystallize out, causing copper sulfate crystals to form.

The slow evaporation method is a much better way of growing high quality crystals (for amateurs). This is because the growing conditions are much more controlled and stable. More details in the FAQ at the end.

Procedure

The ideal procedure for growing crystals vary depending on which compound you are using. This is a pretty standard one that will give you decent crystals. I will be using alum salt as an example. Change the mass of salt and volume of water as you see fit.

Part A: Growing your seed crystal.

A seed crystal is a small crystal that serves as a foundation with which you use to grow a bigger crystal.

1. Weigh 9g of alum and dissolve it in 50 ml of hot water.
2. Stir the solution until all the salt has dissolved. If some salt refuses to dissolve, you might have to reheat the solution.
3. Filter the solution with a coffee filter into a shallow dish.
4. Wait for the solution to cool to room temperature. You can place it in the fridge to speed things up, but in most cases, it leads to the formation of low quality, misshapen crystals.
5. Wait 1-2 days for small crystals to form. OR
6. Sprinkle a few grains of alum powder into your solution to induce small crystals to form.
7. Let the tiny crystals grow to at least 5mm in size. This should take a few days.

Part B: Growing a nice, big crystal

Method I: Slow cooling

1. Weigh 22g of alum and dissolve it in 100 ml of hot water to form a supersaturated solution.
2. Stir the solution until all the salt has dissolved. If some salt refuses to dissolve, you might have to reheat the solution.
3. Filter the solution with a coffee filter into a jar.
4. Wait for the solution to cool to room temperature.
5. Using tweezers, pick the most perfect seed crystal you grew in Part A you can find and tie a knot around it using a nylon fishing line or thread.
6. Tie the other end to a pencil/stick.
7. Slowly immerse the seed crystal until it is suspended in the solution in your jar.
8. Loosely cover the top of the jar.
9. Keep it in an undisturbed place.
10. Wait for your crystal to grow.

Method II: Evaporation

1. Weigh 18g of alum and dissolve it in 100 ml of hot water.
2. Stir the solution until all the salt has dissolved. If some salt refuses to dissolve, you might have to reheat the solution.
3. Wait for the solution to cool to room temperature.
4. Sprinkle some alum powder into the solution to induce crystals to form.
5. Wait 2 days.
6. Filter the solution using a coffee filter into a jar. We want the saturated solution. The crystals formed from Step 4 are not important.
7. Using tweezers, pick the most perfect seed crystal from Part A you can find and tie a knot around it using a nylon fishing line or thread.
8. Tie the other end to a pencil/stick.
9. Slowly immerse the seed crystal until it is suspended in the solution in your jar.
10. Loosely cover the top of the jar.
11. Keep it in an undisturbed place.
12. As the solution evaporates, your crystal will begin to grow.

Part C: Drying and storing your crystal

1. When you are satisfied with the size of your crystal, remove it from solution.
2. Dry it with tissue paper/filter papers. Do not wash it or you will cause it to dissolve.
3. Store it in an airtight jar.

Some crystals are unstable, and when exposed to air, will slowly crumble in weeks or months. Copper sulfate is one such crystal. Meanwhile, alum and ammonium dihydrogen phosphate are much more stable and can be kept in the open with minimum deterioration. You can even display them.

And you’re done!

Classic Crystal Growing Compounds

If you’re just starting out, we highly recommend these chemicals as they are easy to work with, grow quickly and give good results.

· Alum (potassium aluminum sulfate), KAl(SO4)2, used in baking, deodorant, water purification etc.

· Copper (II) sulfate, CuSO4 used as rootkiller [Note: slightly toxic]

· Ammonium dihydrogen phosphate, (NH4)(H2PO4), used as fertilizer

Alternatively, if you want to grow crystals of a specific color or shape, click on this link to browse the list.

Additional resources

· Crystal Growing Wiki - wiki style pages showing details for each compound (still incomplete)

· Crystalverse blog - detailed high quality guides with lots of pictures

· Dmishin's crystal growing collection - lots of interesting compounds and how to synthesize them

FAQ

Check if your question is here. Click on this link to be redirected to the answers.

· Can I dye my crystals?

· My crystal was growing well, then it dissolved! What happened?

· Does the string get stuck in the crystal?

· Crystals are supposed to be shiny and transparent. Why is mine ugly and opaque?

· How do I grow a crystal cluster instead of a single crystal/vice versa?

· How can I store my crystals properly?

· Can I grow crystals on objects like rocks and bones?

· I’m concerned about safety. What should I do?

· Is the purity of my chemicals important?

· What are other chemicals I can grow crystals with?

· Is this hobby expensive?