How to make quick crystals

How to make quick Crystals

Every summer when I declutter my science supplies cupboard I come across a few hidden treasures. (The reality: “Oops, we never did get around to making shadow leaf prints / home made light bulbs / popsicle stick trebuchets,” accompanied by a pang of guilt. Is that just me?)

The Epsom salts were bought to make bath fizzies with C(11) last Christmas. The fizzies never happened, but on the bright side, we had an unopened pack of Epsom salts when CSIRO’s cool crystals email landed in my inbox.

J(10) asked if Epsom salt was like the stuff we put on our fries, which was a good opportunity to remind ourselves what we learned about salts when we concocted our own fizzy drinks a few months back: A salt is created when an acid and a base neutralise each other.

Epsom salt is another name for magnesium sulfate. We looked up magnesium and sulfur in our book, The Elements, and noticed how very different the salt is from its constituent elements.

Easy Crystals - equipment
All you need to make quick crystals

What you need

Epsom salt (1/2 cup)

Hot water (1/2 cup)

Food colouring (optional)

Glass, spoon

What you do

Put the salt and water in the glass together with a few drops of food colouring. Stir for about five minutes, then put the glass in the fridge for at least three hours.

How to make quick Crystals
Dissolving the Epsom salts

What happens

After just a few hours in the fridge, you get beautiful crystals like these.

How to make quick Crystals
Epsom salt crystals

We carefully drained the water to get a better look at our crystals.

How to make quick Crystals
Taking a closer look at the crystals

How do crystals form? The scientific explanation

Epsom salt is an ionic compound. It’s made up of magnesium and sulfur ions joined together by ionic bonds. When we dissolve the salt in hot water, these bonds break and the two elements become separated .

Later, when we cool the salt solution in the fridge, the magnesium sulfate ions no longer have enough energy to move about freely. The ions begin to re-bond, first as single molecules and then – as the molecules themselves begin to join together – as crystals.

Science Kids at Home has some cool diagrams showing what’s happening at a molecular level.

How to make quick Crystals
Epsom salt crystals

More crystal science

Different types of molecule always the same shape of crystal, every time they form.

In the past we’ve also made crystals from table salt (sodium chloride), borax and sugar. The process for each of those is slightly more fiddly, but comparing the different shaped crystals is interesting. Borax crystals make pretty decorations, and sugar crystals are yummy!

Sugar crystals
Sugar crystals
Salt crystals
Salt crystals
Borax crystals
Borax crystals

And now the Epsom salt packet has been opened, we’re one step closer to making those bath bombs. 🙂


I’m appreciatively linking up with Weird Unsocialised Homeschoolers’ Weekly Wrap-Up and All Things Beautiful’s Science Sunday.

How to make quick Crystals

How to make quick crystals

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19 thoughts on “How to make quick crystals

  1. You are not alone in pangs of guilt over unused science supplies. In fact, your post reminds me we still have over half a crystal growing kit left to use and I never got around to making rock candy after buying some fun molds. Great discussion of salts and ions.

    1. Thanks, Carol. I’m hoping I got the science mostly right! I find writing these posts helps me understand what’s going on better than anything. We don’t always go into the chemistry in great detail (yet) but knowing it myself means I’m prepared for questions – and the future! Ooh – fun molds – maybe we should get some of those…

  2. The crystals are beautiful! I really like how you’ve shown the different types of crystals formed by using different materials. We tried to make some from sugar but that didn’t work. We’ll probably try again at some point.

    I have many unused/half-used supplies that I’m slowly working our way through, so you’re definitely not alone in this!

  3. Awesome! We have Epsom salts too; maybe we’ll try it this coming week. We always seem to have “leftover” science kits and art kits that we forget we ever got. I always feel guilty for forgetting about them but love knowing I’m going to find something new every time we clean out the school closet!

    1. That’s a great way of looking at it, Joanne, yes! Do try Epsom salt crystals – I couldn’t believe what an instant win they were compared with the other crystals we’ve made.

  4. We’ve tried making crystals many times and have never had good luck. I’m giving this one a try since we’ve never used epsom salts. Maybe that will work better than the alum we always used before. Thanks for sharing at Weird Unsocialized Homescoolers.

    1. This one really is much easier than the other ones we’ve made, Erin – do give it a go. One set of crystals formed faster than the other, but they both got there in the end. We’ve never tried with allum – sounds like a challenge!

    1. Weirdly, crystals seem to be something that work for us. (Just don’t talk to me about electric lemons.) But this sort were super-easy and fast so do give them a go some time.

  5. I might give these a go. Like Ticia, we haven’t had much luck with crystals despite having a kit which promises the most amazing fail-safe crystals. They obviously didn’t pre-test with someone like me at the helm because ours failed!

    1. I think it’s probably a good thing we’ve never tried one of those ‘fail-safe’ crystal kits, Claire. From the sound of it they don’t sound very reliable!

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