Looking for a last-minute Valentine’s activity? There’s still time to make these pretty crystal hearts.


You’ll need: mason jar or other heat safe cup or container, pipe cleaners, something to suspend the pipe cleaner in the jar (string or another pipe cleaner and pencil), water, and Borax

  1. Bend a pipe cleaner into the shape that you want to create. We did hearts for Valentine’s Day, but you can do anything that you want here. (Tip: it can be helpful to bend the pipe cleaner around a cookie cutter.)
  2. Bend one end of the pipe cleaner (or tie one end of a string) around your bent pipe cleaner and the other end around a pencil, so that the pipe cleaner will hang in the middle of the container. Check the depth and then remove from the jar.
  3. Heat water to just under boiling and remove from heat. Add borax and stir to dissolve. Start with about 3 Tbs. per cup of water and then add 1 tsp at a time until you can’t dissolve anymore and you see a little bit start to settle at the bottom. (You might not need to add any extra after the 3 Tbs. per cup.)
  4. Pour this solution into your mason jar.
  5. Carefully dip your bent pipe cleaner into the water solution
  6. Let cool and check on it over the next few hours. Let sit overnight.



Here is what’s going on: What you are seeing is the process of crystallization. Crystallization is a technique that separates a solid chemical from the liquid that it is dissolved in (and possibly other solids that may also be present in the liquid). Borax contains the solid chemical that we are working with here and it is called sodium borate. (The chemical formula is Na2[B4O5(OH)4]·8H2O.) One of the characteristics of the chemical solid that relates to crystallization is its solubility. Solubility is how much of something you can dissolve into a solution – sodium borate in the water, in this case. Because we kept adding sodium borate until we couldn’t dissolve anymore, we formed what is called a saturated solution. This means that the water is holding as much of the chemical as it possibly could. (If you add more it just settles at the bottom instead of going into solution.) For most things, the solubility increases (more can dissolve) at higher temperatures. Because we heated the water before we formed our saturated solution, we were able to get more sodium borate to dissolve than we would have been able to if the water was at room temperature or cold. What this also means is that there will be too much sodium borate for the water to hold as it starts cools. As the water starts to cool, some of the sodium borate will come out of solution and it will organize into a highly ordered structures as it does. These highly arranged solid structures are called crystals and they settle on the pipe cleaner and the sides of the jar. More and more molecules can be deposited on this ordered structure as the water continues to cool and eventually the entire pipe cleaner will be covered, leaving you with a very pretty science experiment.