Alum, found at the grocery store, can form beautiful diamond shaped crystals.
The best part is, anyone can grow some within a few days at home!
It is also beginner friendly, easy to grow and completely non-toxic. You can have your first specimen in a week or two.
Of course, trying to grow extremely high quality crystals will take some skill and patience. But it can be done – and in this guide, I will walk you through the steps to do exactly that.
This guide will be divided into 4 easy-to-follow parts as shown below:
- Preparing the growing solution
- Growing a seed crystal
- Growing a big alum crystal
- Drying and storing the crystal
Preparing the growing solution
To grow our alum crystal, we first need to prepare the solution for it to grow out of. Think of it as something like salt water. When salt solution evaporates, salt crystals are left behind. Similarly, when alum solution evaporates, alum crystals are left behind.
- Dissolve 60 grams of alum powder in 500 ml of hot water. Stir the solution using a spoon until all of the alum dissolves.
- Filter the solution with a coffee filter to get rid of any dust. Tissue paper also works.
- Wait for the solution to cool to room temperature.
Growing a seed crystal
After cooling, sprinkle a few grains of alum powder into the solution. Tiny crystals should start forming in the solution within 30 minutes.
This is where my guide differs from others you can find online.
Do not be tempted to grow these small crystals. Leave the solution alone for 2 days. This step will ensure that you get more beautiful crystals in the end.
Low quality alum crystals that formed at the bottom of the container.After 2 days, pour 50 ml of the alum solution into a flat dish, and the rest of the solution into a transparent jar/cup. You only want the solution – leave the crystals at the bottom of the original container behind.
Leave both the dish and the cup containing the solution in an undisturbed place. Beautiful crystals will start forming.
After a few days, your dish will contain many small, clear crystals. Once the crystals reach 0.5 cm in size, select the most beautiful crystal inside the dish.
Excited? I bet you are!Then, tie the crystal to a fishing line (or a string), taped to a stick.
Lower the seed crystal into the cup containing the remaining solution.
Place the cup in an undisturbed place, and all you need to do now is to wait!
Alternatively, if you don’t want to tie the crystal to a string (because it will get stuck inside, you can also grow your seed crystal at the bottom of the same cup/container. Here’s an example:
Growing a big alum crystal
As the solution evaporates, alum particles will be deposited on your seed crystal.
Therefore, it will slowly grow larger.
You can stop growing it when:
- You’re satisfied with its size
- The level of the solution has decreased so much that it’s about to expose the crystal
You never want the crystal to be exposed. Otherwise, its surface will no longer be smooth and clear.
An example of a crystal that waited too long until all the solution had dried up.Regardless, when you want to stop growing, take it out, and dry it using a piece of tissue paper (filter papers are better). Do not wash the crystal or you will cause it to re-dissolve.
And that’s it, you’re done!
Storing the crystal
If left in open air, your alum crystals might slowly turn white over time. This is because alum crystals have water molecules trapped inside their crystalline structure, and as that water dries up, the crystal turns white.
To prevent this, keep the crystal in an airtight container. Better still, keep it with some alum powder. The alum powder will sacrifice itself, and in turn, provide a stable atmosphere inside the container so that your main crystal does not dehydrate.
That’s all for this guide.
Growing crystals takes time, but with patience and a little bit of luck, you can definitely create sparkling gems at home.
An alum crystal acting as a prism in the morning sun.Curious about the science behind crystal growing? Check out this article to learn all about it! (Work in progress, available soon!).
If you have any questions, feel free to put them down below.
Alternatively, check out how I grew crystals that looked like coral using nothing but limestone and vinegar here.
Happy growing!
Can you coat the crystal in a clear
nail polish to preserve it?
Absolutely. That is indeed a good way of preserving the crystals.
It almost looks like you added Borax to prevent the octahedral structure from taking over the cubic structure completely. Did you add anything to get that effect or did it just occur naturally?
Good observation! Unfortunately, no I did not. Maybe it was because I was using food grade alum, and impurities inside it affected the growth of the crystals in a similar way to borax.