Frosted window panes conjure up Christmas carols and seasonal festivity. But if winter isn’t cold enough (or your house isn’t drafty enough!) to leave an icy layer of frost on windows, make your own! In this super-simple science project, use Epsom salt crystals and frost your windows even if its hot outside!

What You Need:

  • magnesium sulfate (Epsom salt), 75 grams (1/3 cup)
  • liquid dishwashing soap, 1-2 drops
  • water, 125 ml (1/2) cup
  • lens cleaning cloth (or similar high-density cloth)
  • 600 ml beaker (or other glass container)
  • stirring rod (or spoon)

What You Do:

  1. Make a supersaturated solution by stirring the Epsom salt (solute) into warm tap water (solvent) inside the beaker. If the salt doesn’t dissolve completely, have an adult help you microwave it for about 30 seconds. Carefully remove it, and stir it again.
  2. Add the dishwashing soap and stir again.
  3. Use the lens cloth to “wash” the solution onto a glass window or mirror. Dab away the excess to avoid drips.
  4. Let it dry and enjoy your homemade “frost!”

What Happened:

A solution consists of two things: a solvent and a solute. In most household solutions, water is the solvent will likely be water. In fact, it dissolve so many different things that it’s known as the “universal solvent” A solute is just about anything that dissolves in water: sugar, salt, soap, some chemicals, hot cocoa mix, etc.

Note that other liquids besides water are solvents as well. For example, if you heat milk on the stove and add sugar and cocoa powder to make hot chocolate, the milk is the solvent and the sugar and cocoa are both solutes.

A saturated solution forms when the solute is added to the solvent can’t be completely dissolved by the solvent. Some of the solvent remains at the bottom of the container or just hangs out in the solution, no matter how much you mix it.

When you heat a saturated solution, the solvent is able to hold even more of the solute. At that point, some or all of the solute that was just hanging out in the solution disappears as it dissolves into the solvent, forming a supersaturated solution! A supersaturated solution can only keep that larger amount of solute dissolved in the solution while it remains at a certain higher temperature, so as the solution cools, it becomes unstable and some of the solute will begin to crystallize back out of the solution as the temperature of the solution lowers. This means that a supersaturated solution is a great place to start when you are trying to grow crystals, just like you did here.

Download the instructions.

how to make a frosted window pane