But one of the easiest and most beautiful crystal you can grow is actually a common fertilizer. It’s called monoammonium phosphate (MAP) and it gives plants the nitrogen and phosphorus they need.
MAP is cheap, non-toxic and under the right conditions, grows into stunning crystal clusters. In fact, it’s the ingredient inside most crystal growing kits. More surprisingly, these crystals are also grown industrially and have military and space applications (more on that later).
There are many guides on growing crystals online, but none of them go into great detail and they don’t show you just how stunning these crystals can be.
I’ve been growing crystals for 3 years now, and I’ve learnt a few tricks to get great crystals.
Some crystals I grew on a small branch overnight. Later, I’ll show you how I made it.
In this article, I’ll cover the best crystals I’ve grown, share the exact procedure I used, and show you beautiful specimens grown by other hobbyists.
Growing crystals at home
The idea is simple. Dissolve the MAP powder in water until it is saturated. Wait for seed crystals to form, and harvest them after a day. Transfer the seed crystals to a bigger container and let them grow.
I’ll go through each step with you.
For growing crystals, you’ll need:
- A packet of MAP fertilizer
- A pot to dissolve the powder
- A jar to grow the crystals in
- A filter funnel/coffee filter
- Some thread/fishing line
- A small dish
- A spoon
- A pencil
You can find monoammonium phosphate (MAP) in gardening stores as a fine white powder. Sometimes, it’s also called ammonium dihydrogen phosphate (ADP). If you can’t find it, you can order some online.
How much MAP you need depends on how big you want to grow the crystal. 500g is enough to grow a crystal the size of your palm. Theoretically, there is no limit to how big you can grow them, provided you have enough solution and a sufficiently large container.
A massive 6.5-pound crystal grown by Terry Bartlett, a long time crystal growing enthusiast.
Some insanely impressive MAP crystals by Spanish artist Isabel Lopez.
This guide will be split into 6 sections:
- Preparing the solution
- Growing seed crystals
- Growing big crystal clusters
- Growing perfect single crystals
- Growing crystals on objects
- Troubleshooting & FAQ
All the steps are very easy to follow.
Preparing the solution
Technically, MAP is a type of salt. Like table salt, it dissolves in water. At room temperature, 100 mL of water can dissolve about 40 g of MAP. Hot water can dissolve more.
Let’s start. First, prepare some hot water. For every 100 mL of water, dissolve 60 g of MAP. Stir until all the powder dissolves. I’m using a beaker, but you don’t have to.
Filter the solution into a jar using a coffee filter to get rid of dust and impurities. Then, leave the solution to cool down.
Growing seed crystals
Once cool, our solution is ready. Now, we want to start growing small crystals to act as “seeds” that will form bigger ones in the future.
First, sprinkle a pinch of MAP powder into the solution, and stir it vigorously. After about 30 seconds, you should see a lot of extra crystalline dust forming. This is exactly what we want.
The dust is actually made of thousands of microscopic crystals that formed when you disturbed the supersaturated solution.
Then, leave the jar alone for 1-2 hours.
When you come back, you’ll find that the dust has formed crystals! Also, there might be some small crystals floating on the surface of the solution.
Give them some time to grow.
The next day, the crystals should look like this:
Pour the leftover solution into another container. After that, remove the chunk of crystals at the bottom of the jar. If it’s stuck, put the jar face down and knock hard to make it come loose. It’s no big deal if the chunk breaks apart.
Now that you have an assortment of small seed crystals, it’s time to grow bigger ones!
Growing big crystal clusters
Don’t discard the leftover solution. It’s perfect for this step.
But what if you don’t have enough solution left?
Easy. Make more.
But this time, we’re making a growing solution. This solution should be less concentrated than the solution we used to grow seed crystals. Growing crystals from this solution makes them clearer and higher in quality.
So, you want to dissolve 45 g of MAP per 100 mL of water. Like before, stir until all the powder dissolves.
At this point, I’d also like to teach you how to control the shape of the crystals. By default, MAP forms thick prismatic crystals. When you make the solution more acidic, the crystals resemble sharp, pointy spikes.
This seed crystal was grown from a more acidic solution. As a result, the spikes are longer and sharper.
A very easy way to increase the acidity is to add alum, used in baking and water purification. It can be found at the grocery store, or bought online.
Depending on how spiky you want your crystals, add anywhere between 0 and 1 gram of alum per 100 mL water.
Dissolve the alum in the MAP solution. Like before, filter the solution and wait for it to cool.
Then, pour the solution into a dish, and gently place a seed crystal in the middle. Since you have so many seed crystals, you might want to do a few of these at once.
This will be your growing setup. Leave it in a sheltered area, somewhere that isn’t directly exposed to the wind or fan.
Depending on your conditions, the seed crystals will start growing within a few hours, and be noticeably bigger within a day. After 3 days, this is what the crystal in the picture above looks like:
Isn’t it amazing, how you can just grow crystals at home?
To give you an idea of how adding alum affects the shape of the crystals, here are some pictures of MAP crystals I grew using the same setup.
Crystals grown with (0, 0.25, 0.5, 0.75, 1 & 1.25) g alum / 100 mL water over 3-6 days.
1 and 2 are quite lumpy, with few distinct crystals. Their number and length greatly increase as more alum is added.
After a few days, your crystals should be decently sized. Select the most beautiful ones, and transfer them to a bigger container filled with the same growing solution (45 g MAP / 100 mL water) and the desired amount of alum.
Place the crystal inside, and wait for it to grow big!
Smaller crystals like to form at the side. They compete with your main crystal for growth, but don’t bother removing them. Attempting to do so only causing crystal dust to form and stick everywhere.
Instead, either a) blow them away with a dropper or b) pour the solution to a new container and move the main crystal there.
Observe how lots of smaller crystals like to form alongside the main crystal. There’s a clear ring in the middle because I blew them away with a dropper.
Once you’re satisfied with their size, you can harvest and dry them on a paper towel. Don’t wash them though, because they will slowly dissolve in water.
Here’s my crystal after 3 weeks:
A star shaped crystal grown with more alum over the course of 3 weeks:
An even spikier one, taking just 1 week to grow:
Note that the more alum is added, the faster the crystals appear to grow. Actually they grow at the same rate; sharper spikes grow longer faster, but individually they contain less crystal mass.
Growing crystals at the bottom of the container means they will always be flat on the underside. If you want to grow more symmetrical clusters, you can hang the seed crystals using a thin nylon fishing line.
The crystals are quite hardy, and it’s safe to handle them. But the crystals on very spiky specimens are sharp and much more fragile – so be careful.
If you’re a parent, watch as your kid falls in love with science. If you’re a kid, show them off, and you’ll automatically become the coolest kid in class.
But wait! There’s more to it.
Growing perfect single crystals
So far, we’ve been growing crystals in the form of clusters.
MAP can also form single crystals that look like gems. Growing them will require a different approach. Here’s how:
Prepare another growing solution. Pour it into a dish. You don’t need to add any powder or seed crystals. Just leave it in a sheltered place for a day or two.
You should notice some clear, individual crystals start to form.
As they get bigger, they will start to grow into each other, which is bad.
So, we want to isolate the crystals by hanging them with a fishing line. Pick them out with a pair of tweezers and tie them onto the line. Tie the other end to a stick.
And here are the results:
Like before, adding alum will make the crystals spikier. Check out this super sharp needle, grown from a solution with 1 g alum / 100 mL water.
Perfectly balanced, as all things should be.
And this beautiful star, consisting a pair of single crystals grown into each other.
They even have a baby.
You might have noticed that these crystals have imperfections on their surface. You can reduce these flaws by growing them under more stable conditions, but the main issue is because the MAP fertilizer isn’t pure.
To get pure MAP, you need to buy lab or reagent grade monoammonium phosphate, which is more expensive. Then the crystals will have perfectly flat edges.
Some very pure MAP crystals I grew.
In fact, we’re not the only ones growing crystals.
MAP crystals are grown industrially to be used in electronics and optics. They also have piezoelectric properties, which means that they accumulate electric charge when hit. It was even the subject of a 1963-1965 crystal research project by DARPA, and massive single crystals of pure MAP are grown by the National Ignition Facility to be used in lasers.
Here’s a picture of one of those crystals from the DARPA project, provided by Reddit user u/tlbmds who obtained it from an estate sale. His post contains more information.
Growing crystals on objects
In this section, we’ll be growing crystals on objects.
First, select something that you want to crystallize. Ideally, it should be rough, and have some bigger features. Stuff like rocks, branches and sculptures. Don’t choose delicate objects with fine features like dandelions. Those features will not be preserved.
Now, prepare 2 solutions, one big and one small, with concentrations 50 g and 60 g MAP / 100 mL water respectively.
Stir, filter and wait for it to cool.
Two solutions. Food coloring has been added to the bigger batch.
Sprinkle some MAP powder into the smaller jar. Stir vigorously to form the crystalline dust. Then, immediately poke your object into the jar to let some of the dust stick on it. Let it stay there for about 30 seconds.
Then, remove it from the small jar, and immerse it into the big jar – and you’re done.
The crystal dust should start forming crystals on the object. Within a few hours, my branch looked like this:
The next day:
Get creative with this process. Here are some ideas:
- Try solutions of different concentrations.
- Try crystallizing smooth surfaces.
- Try gluing the seed crystals on the object.
- Try not using seed crystals
- Try immersing the object in stages.
- Try growing crystals from a solution without alum, then place them in a solution with alum. And vice versa. This one is very interesting. What do you observe?
Here are some beautiful specimens from the crystal growing community.
A crystallized cicada by Adrienne DeLoe, who specializes in preserving insects through art.
Another gorgeous cluster of orange crystals by Isabel Lopez.
Troubleshooting & FAQ
There are a few places where things might go wrong. All of them are easy fixes. They also apply to crystal growing kits that you buy at the store.
Why are crystals not forming?
Try dropping a pinch of MAP powder into the solution and see if crystals form. Sometimes they need something to kick start their growth. Otherwise, it’s possible that your solution is not concentrated enough. Either reheat the solution and add more MAP, or pour it into a flat dish to speed up evaporation.
Why did my crystals dissolve?
This occurs when you put an existing crystal into an undersaturated solution (same problem as above). I recommend preparing large batches of solution at once, so that you don’t have to keep worrying about this issue.
Why are my crystals not transparent?
The crystals grew too quickly. The supposedly perfect crystal lattice structure contains lots of defects as a result. Your solution was likely too saturated. Reduce the concentration of the growing solution from 45 to 40 g MAP / 100 mL water, or even lower (if you live in a cold climate).
Why do my crystals look like an ugly clump?
Same problem as above. Also, make sure the solution does not become too low until it exposes the crystal to the air. Stop growing or add more solution before this happens.
What is this weird crust creeping up my container?
Air movement causes crystals to form above the surface, on the walls of the container. It then sucks up more solution, growing upwards. This effect seems to increase with the addition of more alum.
Aside from slowing down evaporation, there’s nothing much you can do about it. Just pour the solution into another container and continue growing. Besides, once you stop freaking out and take a closer look, they’re kinda beautiful.
Why are crystals not sticking to the object?
Your solution is not supersaturated enough. If the 60 g MAP / 100 mL nucleation solution doesn’t work, go for 70 g. If it still doesn’t work, the surface of your object is probably too smooth.
What is the recommended amount of alum to add?
It depends on your taste. But use less alum (< 0.25 g alum / 100 mL water) if you want super clear single crystals, and use more alum (> 0.5 g alum / 100 mL water) if you want well defined crystal clusters. Doing the opposite will encourage the growth of jagged single crystals and formless white clumps respectively.
Why did white stuff form after adding alum?
Your water / MAP fertilizer likely contains impurities. One of the uses of alum is to remove impurities from water by precipitating them out. It’s annoying, but nothing to worry about. Filter it away, and continue growing crystals.
What is the issue with food coloring?
It’s tricky to dye the crystals. The food coloring you use might react with the solution in unexpected ways. My purple food coloring turned blue in the solution. I can’t give much advice here, because every brand of food coloring is different. I’ve heard of people using vegetable carbon, cochineal, even highlighter ink. Feel free to experiment, and remember to stay safe.
Can I make jewelry with these crystals?
No. The crystals are too brittle and cannot be polished. They have a Mohs hardness of around 3. They also dissolve in water. You wouldn’t want a water soluble gem to be a symbol of everlasting love, do you?
Nail polish gives an additional layer of protection. Some people have suggested sealing it in epoxy resin. I haven’t tried it before, but it might work. Let me know if it does.
Being naturally air stable, they do make for good decorations.
What other crystals can I grow?
After growing crystals for years, I’m constantly amazed by this hobby. I recommend trying out alum (yes, alum by itself can grow into stunning octahedrons) or sugar. Or take a look at how to grow sodium chloride crystals.
That’s all for this guide. If you enjoyed it, share it with your friends! If you have any questions, feel free to comment or send me a message. I’d love to have a chat.
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And as always, happy growing.