Crystal Growing Experiment

crystal growing experiment

Let me show you what we have put in our Christmas Tree.

growing crystal experiment ornament

Do you feel like making yours? We will show you how to do it, because it is also an experiment, in this case, to investigate on crystals and crystallography.

You need alum (potassium aluminum sulfate), water and some pipe cleaners. We bought alum here, but maybe you know any other shop where you can find it.

You need to heat some water (not necessarily boil it) and dissolve 2 tablespoons of alum, and stir until it is completely dissolved. Then add some more alum, and stir again until saturation (when no more alum can be dissolved). You need to separate then the liquid from the solid on the bottom, by pouring the solution into a new jar.

Now, with the pipe cleaner form the shape you like most: a snowflake, a star, a spiral… Then, you need to suspend the pipe cleaner in the solution (you can tie a piece of string or just leave a longer side of the pipe cleaner, and tie it to a craft stick that will rest across the top of the jar). Leave the solution undisturbed for some hours and see the results.

growing crystal experiment result

Some other crystals need some days to grow, but in this case, it is really quick and you will see the crystals being formed in only some hours. But there are many factors that affect the growing process. We suggest you try it, investigate, and tell us your results.

For example, we had the crystals we have seen at the beginning of the post, but in one of our tests, the pipe cleaner had only 3 or 4 crystals attached to it, but some quite big crystals appeared on the bottom of the jar.We have put them in order to observe their shape and compare their size.

growing crystal experiment macrocrystals

We have created 2 beautiful pendants with those.

growing crystal experiment pendant

The advantage of using this sulfate is, as we said, the high growing speed and the large number of crystals that grow on the pipe cleaner. But you can also try other substances easier to be found such as salt, sugar, sodium bicarbonate, etc and compare your results.

Remember our rock candy?. The process to make them is very similar, but using skewers instead of pipe cleaners for the crystals to grow on, and it takes a bit longer.

What is the science behind?

In order to make a crystal growing experiment, you need a saturated solution. That is a solution where, for a certain volume of solvent (water), and at a certain temperature, you have the maximum quantity of dissolved solute (alum), You will know you reached this maximum when no more substance can be dissolved (it goes to the bottom of the jar). A supersaturated solution is the one which contains more dissolved substance than it can at a certain temperature. In your experiment, you get this supersaturation when lowering the temperature of the solution (you let it cool), and when part of the water evaporates (you leave it uncovered). A supersaturated solution is unstable, and the excess solute precipitates as a crystal. Crystals grow better in irregular surfaces. That’s why they grow on the pipe cleaner inside the solution.

Want to find more ideas about crystal growing? You can take a look at our “Crystallography” board in Pinterest

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