Cut out various shapes from different colours of construction paper. Salt crystals will technically grow right on the baking sheet without paper, but it's more fun to see them on colourful shapes!
Place the shapes on a baking sheet.
Step 2: Make the supersaturated solution
Add 1/4 cup sea salt to 1-1/2 cups boiling water.
Stir well to ensure as much salt as possible is dissolved into the water.
If all the salt is dissolved keep adding more salt, 1 tablespoon at a time. Stir well and keep adding salt until no more can be dissolved.(You can stop adding salt when you can see undissolved granules in the bottom of the measuring cup.)
Step 3: Add solution to the tray
Pour the supersaturated solution over the construction paper shapes. Try not to get any of the undissolved salt (from the bottom of the measuring cup) on the tray.
Adjust the shapes on the tray so they're not touching - they'll stick together if they dry out while touching.Be careful! If your water is still hot, use a utensil or stir stick to move the shapes around.
Leave the baking sheet in an undisturbed area and wait for the crystals to grow.
You should have full crystal growth after 2 - 3 days.
Your salt crystals are complete!
Video
Notes
If crystals are growing on the shapes and you still have a lot of water on the tray you can carefully pour off the extra water and let the shapes dry out.If you don't have many crystals growing after a couple days, you can pour off the first solution and add a new supersaturated solution to the tray.