Salt. It’s a rock you can eat! You’d literally die without it. And it makes just about everything taste better. Humans have been harvesting salt since prehistoric times. In this edible hands-on activity that’s worth its salt, kids can turn everyday kosher salt into chunky, flaky salt that’s ready to sprinkle on their favorite foods.
Be a Salt Farmer
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Before You Begin
We recommend using distilled or filtered water in this recipe, as tap water can contain tiny dissolved minerals that get left behind when the water evaporates (but are safe to drink). They can give your salt a bitter flavor. You’ll add the kosher salt to hot water in 1-teaspoon amounts—there are 6 teaspoons in 2 tablespoons.
- ¼ cup distilled or filtered water
- Liquid measuring cup
- Oven mitts
- 1-teaspoon measuring spoon
- 2 tablespoons kosher salt
- Coffee filter
- 8-inch square glass baking dish or pie plate
- Hand lens or magnifying glass (optional)
1. Add water to liquid measuring cup. Heat in microwave until water is steaming, 1 to 1½ minutes. Use oven mitts to remove measuring cup from microwave (ask an adult for help).
2. Add 1 teaspoon of salt to hot water. Stir with spoon until salt is completely dissolved and water is clear. Continue adding salt, 1 teaspoon at a time, and stirring until all salt is dissolved into water. (If there are undissolved salt crystals after you’ve added all the salt, strain the solution through the coffee filter before continuing with step 3.)
3. Set baking dish in place where it won’t be disturbed. (A warm, sunny spot will help speed up evaporation.) Carefully pour salt water into baking dish.
3. Observe your results: Leave baking dish undisturbed for 24 to 48 hours, or until all water has evaporated. Use hand lens (if using) to observe salt water a few times as it evaporates. What do you notice?
5. Harvest your salt! Use spoon to gently scrape salt from bottom of baking dish (salt will form large chunks). Sprinkle it on finished dishes, such as eggs, vegetables, meats, and more. (Salt can be stored in airtight container indefinitely.)
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Where Did Those Salt Crystals Come From?
The big square or rectangular salt crystals you harvested came from the tiny crystals of kosher salt you started with! When you dissolve salt in water and then let the water slowly cool and evaporate, the structure of the salt crystals left behind can change.
When mixed with water, salt crystals dissolve into tiny ions. The hotter the water, the more salt you can dissolve into it. When dissolved salt ions find one another, they lock together, kind of like puzzle pieces, and fall out of the solution. As more salt joins them, the salt crystal grows bigger and bigger. The slower a salt solution cools, the more time the salt ions have to find one another and grow larger crystals. Since you let your salt solution cool slowly, you were able to form some big salt crystals!
Salt does some powerful stuff in the kitchen. It can take bland chicken breasts and make them juicy and perfectly seasoned in Pan-Seared Chicken Breasts with Chimichurri Sauce. You can also watch a sprinkle of salt pull enough water out of shredded zucchini to create Cheesy Zucchini Crisps that live up to their name.