1. Poke 4 small holes in the bottom of a plastic cup. 2. Place the cup on a saucer. 3. Cut a simple shape from a piece of sponge. For example, you might make the shape of a shell or a bone. The shape will need to be small enough to fit horizontally inside the plastic cup. 4. Add about 3 cm of sand to the cup. 5. Set the sponge shape on top of the sand. Add 6 cm of sand. 6. Mix 4 tbsp. of bath salts with 4 tbsp. of warm water. [Important! The bath salts must contain the mineral magnesium sulfate for this activity to work properly!] 7 Pour the mixture into the cup, and then set the cup on a windowsill or another warm location. 8. Every day for five days, mix 4 tbsp. of bath salts with 4 tbsp. of warm water. Add the mixture to the cup. 9. Allow the material in the cup to dry completely. 10. Carefully remove the sponge shape you made. + Silt Step 4: Record your observations: EDUCATION