Quick answer
Dissolve table salt in hot water until no more dissolves. Hang a string in the solution and wait days to weeks for crystals to form on the string.
Key takeaways
- Dissolve table salt in hot water until no more dissolves. Hang a string in the solution and wait days to weeks for crystals to form on the string.
- Heat 2 cups water until very hot, not boiling.
- Cover the jar with a paper towel and set it in a quiet spot.
Make a Supersaturated Solution
Heat 2 cups water until very hot, not boiling. Stir in table salt by the tablespoon until crystals stop dissolving and sit on the bottom. You need a saturated solution with a little undissolved salt as seed material.
Prepare the Seed String
Tie a clean cotton string to a pencil. Wet the string, roll it in dry salt, and let it dry. This seed coating gives crystals a place to start. Lower the string into the jar without touching the sides or bottom.
Crystal Growth Over Time
Cover the jar with a paper towel and set it in a quiet spot. Crystals form over days to weeks as water slowly evaporates. Larger, clearer crystals need still air and stable room temperature. Bump the jar and growth may stop.
What You Are Observing
Salt dissolves better in hot water. As the solution cools and water evaporates, dissolved salt comes out of the liquid and stacks into cubic crystals. This is the same process that forms rock salt deposits underground.
Step-by-Step
- Heat water
Warm 2 cups water in a heat-safe container. Hot tap water works if an adult handles the pour.
- Dissolve salt
Stir in table salt until no more dissolves. Leave a small layer of salt crystals at the bottom.
- Set up the string
Tie a salted cotton string to a pencil. Rest the pencil across the jar mouth so the string hangs in the liquid.
- Wait and observe
Place the jar where it will not be shaken. Check daily for crystal growth on the string.
- Harvest crystals
Lift the string when crystals reach the size you want. Let them dry on a paper towel before handling.