Quick, Easy Crystals

This week's experiment is simple, and delightful. We will grow some beautiful crystals. Often, growing crystals can be a fairly long, involved process, but this method is incredibly easy. To try this, you will need:

- a disposable plastic or paper cup
- epsom salts
- water
- a refrigerator
- paper towels

Place 1/2 cup of epsom salts into the cup. Then add 1/2 cup of HOT water. You don't want the water to be boiling, but you want it to be hot enough that it is uncomfortable to put your finger in. Our hot water heater is set pretty high, and that worked well, straight from the faucet. If your hot water is set lower, heat it in the microwave for about 30 seconds or so. Don't heat the water in the plastic cup, as the cup will melt and make a mess. (That is the voice of experience talking!)

Stir the hot water and epsom salts well, to allow most of the salt to dissolve. It should not all dissolve. If it does, add a little more. When it is well stirred, place it in the refrigerator, with a small sign saying "Danger! Science experiment!" or something similar, to be sure that no one drinks it.

After three or four hours, examine the cup. You should find that the bottom of the cup has a beautiful cluster of needle-shaped crystals. At that point, carefully pour the water into the sink. Then cut the side of the cup, to allow you to lift the crystals out of the cup. Place them on a couple of folded paper towels to let them dry. If they fall apart, or if you are not pleased with the result, put them into another cup of hot water, and try again. You can regrow the crystals over and over.

OK, so what is happening? Solubility (the amount of something that will dissolve) is tied to temperature. The hotter the water is; the better it is at dissolving the epsom salts. If you had a way to see the atoms along the edge of the crystals, you would notice that some of magnesium sulfate (epsom salts) was constantly leaving the crystal to dissolve in the water, while other bits of magnesium sulfate constantly leaving the water to join the crystal. If everything balances, then the crystals stay the same size.

On the other hand, if the water is hot, the extra energy lets more of the salt leave, throwing off the balance. That means that the solid epsom salts will dissolve, until it reaches a new balance. At that point, the salts stop dissolving.

When you put the cup in the refrigerator, heat energy from the cup moves to the surrounding area. With less heat energy in the water, the balance shifts again. Now you have more epsom salts joining the crystals, so the crystals grow. This will continue until things reach a new balance. At that point, the crystals stop growing.

If you want to experiment further, you can continue to play with that balance point. Once your crystals have grown, pour off the water. In another cup, mix another batch of hot water and epsom salts. This time, wait until the water cools almost to room temperature, and then carefully pour it into the cup with the crystals from your first experiment. This time, do not stir! Put it in the refrigerator.

If you get the balance right, then your original crystals will not redissolve completely. As the solution cools, more magnesium sulfate will be added to the original crystals, causing them to grow larger. You can try repeating this several times. If your balance is off, and the crystals dissolve, then just heat the water again, and start over. When you are done, you can let the crystals dry and put them on your shelf. If they get broken or dusty, just dissolve them, and grow them again.

Have a wonder-filled week.

Anonymous wrote on Mon, 05/06/2013 - 12:01:

I tried making my crystals with a sugar solution and have been waiting for days.My crystals are due tomorrow only thing is not 1 crystal has formed. I've just used your method and am keeping my fingers crossed. I hope to see results within the next 3 hours

Anonymous wrote on Fri, 01/04/2013 - 20:20:

My crystal seems like clear water after about ten minutes when I made it. Is there something wrong with it?

rkrampf wrote on Fri, 01/04/2013 - 21:40:

Be sure to use HOT water, and measure everything carefully. If you still run into problems, add a little more epson salts and try again.

Anonymous wrote on Wed, 05/02/2012 - 07:27:

Grrrrrrrrr! It won't work! LOL! Can anyone give me tips to what I'm doing wrong? Thanks!

rkrampf wrote on Thu, 05/03/2012 - 11:31:

Hmm. First, be sure that you are following the instructions, especially with the measurements. Be sure that you use HOT water, and give it a good stir. Almost all of the epsom salts should dissolve. If you still have a lot of undissolved crystals, then your water was not hot enough. If it all dissolves, then add a little more and stir again. You want just a few undissolved crystals at the bottom.

If that does not work, let me know what is happening after it has been in the refrigerator. Do you have any crystals at all? Does the entire thing crystallize? The more you can tell me about what is happening, the easier it will be for me to figure out what is wrong.

Anonymous wrote on Sun, 05/13/2012 - 05:43:

Same here, mine won't form at all. After I leave it in the fridge for 3 hours, it's still relatively clear liquid, there's nothing in the water.

rkrampf wrote on Mon, 05/14/2012 - 20:19:

Start with 1/2 cup of HOT water and 1/2 cup of Epsom Salt. There should still be a few crystals in the bottom after you have dissolved as much as you can. If all of the Epsom Salt dissolved, then you need to add more.

Be sure that you are using Epsom Salt (Magnesium sulfate). The kind of salt you put on food will not work.

Anonymous wrote on Fri, 02/04/2011 - 13:32:

Making crystals using the science topic 'Dissolving' is very useful.
This website is wonderful!!!

Anonymous wrote on Fri, 12/03/2010 - 18:26:

thank you so much it actually worked i thought it was gonna be a disaster, im trying to get extra credit with my science teacher