Materials

1. Plastic bowl
2. Pieces of charcoal, brick, tile, sponge, or cement
3. Water
4. Table salt
5. Liquid bluing (found with bleaches at grocery stores)
6. Food coloring
7. Measuring tablespoons
8. Masking tape
9. Pens

Procedure

1. Place the piece of charcoal, brick, tile, sponge, or cement into the bowl.
2. Pour two tablespoons of water and two tablespoons of liquid bluing over the charcoal or other material you've chosen.
3. The next day add two more tablespoons of salt.
4. On the third day, pour in the bottom of the bowl (not directly on the base material) two tablespoons each of salt, water and bluing then add a few drops of food coloring to each piece of base material.
5. A crystal formation should appear by the third day. If not, it may be necessary to add tow tablespoons of household ammonia to aid the growth. (Only adults should handle the ammonia.)

What's Going On?

Just as the water, bluing, and dissolved salt combined to form crystals, coral polyps use dissolved calcium carbonate to create the stony cup that protects their soft bodies and creates reefs.