How to Grow Salt Crystal Trees

This experiment shows how salt crystalizes much as it does along the ocean.

Crystal salt tree formations are a classic chemistry project that is fun and instructive. It is chiefly an experiment to demonstrate the qualities of evaporation and salt crystallization. The Dead Sea has huge quantities of salt suspended in water and at the shores the same evaporation takes place. In this project the iron in the bluing and the salt are left behind when the water evaporates. They are no longer suspended in solution and are carried up into the sponges to "bloom" on the surface. The experiment is very simple to put together and is safe for children; however an adult should always supervise and explain any project using chemicals.

Things You'll Need

• Bowl
• Pieces of sponge
• Small bowl
• 4 tbsp. water
• 6 Tablespoons salt
• 4 tbsp. bluing
• Food coloring
• 2 tbsp. ammonia

Instructions

1. Place small pieces of sponge in the bowl. The number and size don't matter, but the more pieces you have the better the shape of the "tree". Don't overcrowd the bowl or there won't be room for the crystals.

2. Pour 2 tbsp. each of water, bluing and salt onto the sponges. You should premix this in a small bowl and then add to the experiment. This is Day 1 and no further activities are required.

3. Add 2 tbsp. of salt on Day 2. Don't be impatient. Nothing is happening until all the liquid is evaporated.

4. Add 2 tbsp. each of bluing, water and salt. Again, mix in the small bowl and pour it over the experiment. Dot each sponge piece with different colors of food coloring. The more colors the prettier the crystal tree will be.

5. Add 2 tbsp. of ammonia if no growth has occurred by Day 4. It will help speed up the process. Be careful and don't breath in the ammonia smell as it can burn your throat and lungs.

6. Continue the process, alternating salt alone and the three ingredients, to keep the project growing. There will be flower like crystals blooming from the tops of the sponges and they will increase until you cannot see the sponge anymore. The dye will color the usually white crystals and turn them pretty pastels.

Tips & Warnings

• The ammonia should be added outdoors and by an adult.

References

• Mrs. Stewart's Bluing: Magic Salt Crystal Garden
• Home Chemistry: Salt Crystal Trees