Chemistry Experiments You Can Do at Home


How can I grow a large crystal?

  • Crystallization
  • Solubility
  • Hot water (from the tap is fine)
  • About 2.5 tablespoons of alum (this is typically found with the spices in the grocery store; it is an ingredient used to make pickles crisp; its chemical formula is KAl(SO4)2
  • 12 H2O)
  • Nylon fishing line or thread (about 15 cm)
  • A pencil or ruler
  • 2 jars
  • Spoon
  • Coffee filter or paper towels
  1. Pour ½ a cup of hot water into a jar.
  2. Add a little bit of alum to the water and stir it in. Try to do this before the water cools down too much. As you’ll recall, we can expect the alum to be more soluble at higher temperatures. We want to create a saturated solution of alum, but we also want to make sure that all of it dissolves. Continue adding alum until it will not dissolve anymore, and then you can add a little bit more hot water to get the last bit of alum to dissolve.
  3. Cover the jar with a coffee filter or paper towel and let it sit overnight.
  4. The next day, pour the liquid into a second jar. There should be small crystals left in the bottom of the first jar. The process of pouring the liquid off of the top of the solid crystals is known as “decanting.” The crystals left behind will serve as the seed crystals to grow a larger crystal of alum.
  5. Pick out the largest crystal, or one with a nice shape that you like. Tie the fishing line or thread around the crystal, and tie the other end of the line to a pencil, ruler, or other long flat object. Adjust the length of the string such that you can use the pencil or ruler to dangle your crystal from the top of the second jar (the one that now contains the liquid) into the liquid without it touching the bottom.
  6. Once your crystal is hanging into the solution, all you have to do is sit back and wait for it to grow. This might take several days. If you notice small crystals growing on the sides or bottom of the jar, it would be a good idea to transfer the solution and your single growing crystal into another jar to prevent the alum in solution from crystallizing into several different crystals (this will ensure that you get a nice big crystal). You can feel free to transfer jars as many times as necessary to continue growing your large crystal.


This is a web preview of the "The Handy Chemistry Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App