Growing Crystals!





Introduction: Growing Crystals!

In this Instructable, we will learn about super saturated solutions, and how to create crystals from them.

(Pictured above is an Alum crystal made using the explained method)

Step 1: Understanding the Science

What happens when we dissolve salt in water? We add a few spoons, keep stirring till all the salt disappears. Salt, here, is the solute and water, the solvent. Together, they form a solution. There is a point when a solution contains more solute than the solvent can dissolve. This solution is known as a supersaturated solution. You normally cannot see the solute in a solution because it is fully dissolved. You are able to see the solute in a supersaturated solution because all of the solute doesn't fully dissolve into the solvent.
Here is a nice graph that I found online, when I was learning more about solutions. We can clearly see that solubility of a particular salt is directly proportional to temperature.So now, we will use the concept of dependence solubility of a solution on temperature to create crystals!

(Please refer:

Step 2: Materials Required

You will need the following to start our experiment:

1. A pair of gloves (optional, but recommended when dealing with salts like Borax)

2. Any salt soluble in water. I have used Borax here. Alternative salts that could be used are Alum, Magnesium Sulphate etc,

3. A cylindrical container, preferably transparent, so it would be easier to check progress without disturbing the system

4. Food colouring! (optional)

5. Water and a vessel that can be used to boil water

6. A scale (just a stick would do), some thread and a pair of scissors.

7. A sieve (optional)

With all this ready, lets move on!

Step 3: Getting the Solvent Ready

Firstly, measure 3/4 of the cylindrical vessel with water (here water is the solvent). Pour the contents into another vessel, one with which we can boil the water. Now, heat the vessel till boil.

Science here: In this step, we boil the solvent in order to increase the solubility of the salt in the solvent, i.e. to create a super saturated solution, which dissolves more salt than at just room temperature.

Step 4: Adding the Solute

Before handling with corrosive / dangerous salts, it is advisable that you glove up!

With a spoon, contentiously add salt to the boiling water. Please note, after the water starts to boil, do not switch of the flame, but leave it in sim and continuously stir will adding the salt.

Science here: There will be a point where you cannot add any more salt and the solution cannot accept any more salt. At this stage, the solution has reached saturation at its elevated temperature, but is at super saturation with respect to room temperature!

After this, switch of the stove, and a SMALL pinch of food colouring of your choice. I haven't done so here, but used green food colour in making those cool Alum salt crystals you saw in the thumbnail.

After doing so, pour the solution from the boiling mixture back into the cylindrical tumbler, through sieve, just to make sure no solid particle passes through.

Step 5: Setting the Core

Once you are done with all the above steps, take a piece of thread of adequate length, and tie it up to the scale / stick as shown. Dip the thread into the solution with the scale supported by the vessel (as shown). It does not matter if the thread floats, but push it in as much as you can.

After doing so, leave the setup at an undisturbed place overnight. By undisturbed, I mean away from vibration.

Science here: The reason we do this is to provide a core foe the crystals to form around; similar to what dust particles do in clouds.

Step 6: Fruits of Labour

After leaving the setup undisturbed for a while, it can be noted that a crystal has grown around the thread! Magical! Now remove the thread from the scale, cut off the excess and create your own crystal garden!

Science here: The reason we let the super saturated solution cool is, because while doing so, the temperature decreases and in turn, reduces the solubility of the solution. So the salt that would dissolve in the solute at a higher temperature, now have nowhere to go, as solubility decreases, so the crystallize out of the solution around the thread (like clouds). This is a gradual and slow process, that is why it is not advisable to store the solution in a fridge to cool, but best left at room temperature. Also, if there are any vibrations / shocks, it would disturb the crystal formation. So, no vibration means better and larger crystals!

You are now endowed with the secret knowledge and science of making super cool crystal! So what are you waiting for? Go ahead and start making 'em!
Arty tip: Use red colour food colouring to make red crystals, and instead of thread, use tin bent in the shape of a heart! You now have a red crystal shaped heart! ( I made this for my mom on mothers day and she loved it :-) )



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    18 Discussions

    good, looking for salt where it make colorful crystals.

    If you doing this with young children, can you substitute sugar for the salt? What kind of sugar would be best?

    8 replies

    I tried it with sugar but it quickly developed mold. You could stop that with a lid but then it might start fermenting and building up pressure.

    If you have regular sugar and water, it will not ferment unless yeast is added. Yeast like you bake with utilizes sugar(glucose) as a nutrient. The breakdown of the sugar causes carbon dioxide to be released thus the bubbles like in beer and champagne. Keep everything sterile, boil the water and sugar to saturate the solution. The boiling should sterilize the solution also allowing the water to become supersaturated with the sugar so it can make nice crystals. Think rock is crystalized sugar. Cover the jar with a clean cloth and you should have no problem.

    Sugar can definitely be used instead of any salt. Regular home - use sugar can be used.
    P.S. the speciel sugar crystal you get is called Rock Candy!

    Does that mean that you could eat the crystals if you substituted sugar?????? COOOOOL!

    Logically, you could!!

    Absolutely the kids can eat the sugar rock candy - would make a good summer experiment for them. I did it when i was a kid and often times see the rock candy in gift shops. Most I see on gift shops are on sticks but we made it using a string


    1 year ago

    This looks awesome. I was wondering if the end result crystal is stable and hard enough to make jewelry (wire wrapped) or will it crumble if I press too hard.

    Thank you for sharing. Dian

    1 reply

    Making jewelry is a really cool idea! But I wouldn't advise so. Salts like Borax produce somewhat weak crystals near the ends of the thread. However, certain salts like alum produce relatively stronger salts. Be warned, dropping any salt from a hieght could possibly break it.

    This is great - I used to love doing this as a kid. I think I usually used a super saturated sodium acetate solution (same reaction as hand warmers).

    This looks really nice! I have some questions:

    1) Why is the salt dangerous before the process but not after? How dangerous is it? Where do you get these salt types? Are they cleaning products or something? Can you use common cooking salt instead?

    2) Can you dip a previously created salt crystal in a new solution and create a larger crystal? Or will it dissolve? I guess it shouldn't because the solution is already saturated, but I'm not sure.

    1 reply

    Actually, rock candy crystals can look a lot like quartz, depending how long you let them grow.

    I will answer your questions to my best ability,

    1) a) Borax salt is amorphous, which means it is "powdery". Since it is powdery, it could probably get easily into your nails or something and that is why it is recommended you use gloves. After it becomes a Borax crystal, it stays a crystal, at room temperature, and its not going to melt, like sugar. So it isn't a problem. Also, since Borax salt is slightly corrosive in nature, gloves are recommended again.
    b) Well, my granddad got these salts for me. He said he got it from depot that sells lab supplies.
    c) I am not quite aware about Borax's cleaning ability, however they seem to sell it for cleaning purposes in other countries. I am not quite sure about it. Please do check it.
    d) One can use any salt, theoretically. I just used borax because it attains super saturation more easily and can produce crystals that are larger and more cooler!

    2) You sure can. That is what I tried on the green alum crystals on the cover picture. If the temperature is not too hot so that they dissolve, the older crystal will act as the core for newer crystals to form, thus making it larger and larger! Really cool if you think about it!