Salt and vinegar crystals are easy-to-grow and non-toxic. You can grow them in a rainbow of colors. This project is especially good for kids or beginners looking for a quick and easy science project.
- Hot water (1 cup)
- Salt (1/4 cup). (Amazon link: Salt)
- Vinegar (2 teaspoons). (Amazon link: White Vinegar)
- Food coloring (optional). (Amazon link: Food Coloring)
- Piece of sponge (Amazon link: Kitchen Sponge)
- Shallow dish
- Stir together the water, salt, and vinegar. Boiling water works best, but very hot water is okay.
- Place the piece of sponge on the shallow dish. Pour the mixture over the sponge so that it soaks up the liquid and just covers the bottom of the dish.
- If you want colored crystals, you can dot the sponge with food coloring.
- Save the rest of the crystal growing solution.
- Set the dish in a sunny window or other warm area with good air circulation. You will see crystal growth overnight or within a day. Add more crystal growing solution to replace the liquid that evaporates.
- Continue growing your crystals as long as you like. The project is non-toxic so when you are done you can either save your crystals or throw them away. You can dump leftover crystal solution down the drain and wash the dish as usual.
Salt dissolves better in hot water than cold water, so as the solution cools the salt wants to come out of solution and crystallize. When you pour the solution over the sponge, this causes the liquid to evaporate. This further concentrates the salt so that it will crystallize. The salt crystals will start to form on undissolved salt or on the sponge. Once the crystals start forming, they grow fairly rapidly.