Wednesday, January 16, 2013

Science Activity

We recently made alum "crystals"!  It was a very simple and enjoyable science project.

If you look really carefully, you can see the "crystal."

Rocks and alum "crystals."

If you are interested in making your own alum "crystals", you will need the following items...
  • Alum (at least 4 ounces, can be found at most drug stores)
  • Two small glasses
  • A spoon
  • Water
  • Pot or some way to heat some water
  • Thread
  • Two weights (we used washers)
  • A large plate
  • Dark paper (we used black construction paper)
  • Magnifying glass
  • Heat some water in a pot until hot, just before boiling.
  • Attach the thread to the weights. (the thread needs to be 2 1/2 times as long as the glasses are high)(Tie a weight to each end of the thread)
  • Pour the hot water into one of the glasses until halfway, mix in alum until you can't get anymore to dissolve.  You will know when you have reached that point when the water remains cloudy no matter how much you stir.
  • Let the mixture stand for a few minutes and the undissolved alum will settle to the bottom of the glass.  Once the solution in the glass is pretty clear, pour some of the liquid into the empty glass.  Be careful, it will still be pretty hot!  Pour as much as you can without disturbing the alum at the bottom of the glass.
  • Put your thread in the second glass and let stand undisturbed for several  hours.(One weight will be in the solution and the other will be outside the glass, on the plate)
  • After several hours observe the thread and you should find "crystals"!  (We put ours on the black paper with rocks, they showed up well that way)
Some options to consider are using sugar instead of alum, this will make edible rock candy!  You could also add food coloring!

*We found this experiment in the "Exploring Creation with 
General Science" book from Apologia.


  1. I need to try this with my boys. It looks easy and fun. Plus, my oldest is really into science right now.

  2. I always loved doing Science experiments! And they usually smell good, too...haha! Enjoy your week!

  3. It was easy and fun!

    Sorry it took me so long to respond, hope you everyone is having a good week!