How to Make a Fossil Sponge

Fossils are the hardened, mineralized representations of the remains of living organisms from the distant past. Fossils can be formed in several ways, one of which is known as permineralization. In permineralization, water gradually dissolves the organic material left behind by a deceased plant or animal, washing it away. Other minerals then fill in the resulting holes. These minerals harden and form crystals, taking the place of structures such as bones. Over time, these crystals replace the entire organism and become a fossil. This process takes nature hundreds of years, but by following the directions below you can use a bath sponge to mimic fossilization in one of two ways---by casting your "fossil" in wax or by forming salt crystals.

Difficulty: Easy

Instructions

Things You'll Need:

• Method 1:
• 1 large bath sponge
• Permanent marker
• Scissors
• Basic bone or shell shape stencils
• 1 block wax, 2-by-2 inches, 6 inches long
• Large pan
• Old coffee can
• Dowel rod
• Rubber gloves
• Goggles
• Tongs
• Food coloring
• Wax paper
• Method 2:
• Large bath sponge
• Permanent marker
• Scissors
• Plastic container, such as recycled yogurt or cottage cheese containers
• Plate
• Sand
• Paper cups
• Warm water
• Bath salts or table salt
• Food coloring (optional)

Method 1, Making a Fossil Sponge With Wax

1. Place the sponge on a flat surface. Use the permanent marker to draw a fossil shape onto the sponge. Make a claw, a wing, and thigh bone or a shell.If you're unsure about your drawing ability, you can use a stencil.

2. Cut out the sponge fossil.

3. Tear off a piece of wax paper large enough to place your fossil on.

4. Place 4 cups of water in the pan (or fill approximately 1/3 of the pan) and place it over high heat. Put the wax into the coffee can and set the can in the pan of water, creating a double boiler. As the water heats up, it will melt the wax.

5. Stir the wax with the dowel rod as it melts.

6. Put on your protective gear: goggles and gloves.

7. Once the wax has melted, add food color if desired and remove the coffee can from the heat.

8. Grab the sponge fossil with the tongs and immerse it in the hot wax. Press the sponge against the bottom of the can to force hot wax into the sponge fibers.

9. Place the sponge on wax paper and allow it to cool.

Method 2, Making a Fossil Sponge With Salt

10. Cut your sponge into the shape of a fossil, as in method 1.

11. Punch a small hole in the bottom of an old plastic container.

12. Place the container on a plate. Then add sand to the bottom of the container, until the sand in the container is 1 cm deep.

13. Place your sponge fossil on top of the sand and pour sand over it, until the fossil is covered by 2 cm of sand.

14. Set three paper cups on the table. Add 3 tbsp. of warm water to each cup. Stir in 3 tbsp. of bath salts or table sale and 3 drops of food coloring if desired.

15. Spoon the salt mixtures over different parts of the sponge.

16. Add more salt water once a day for 5 days in a row.

17. Wait 2 days after the last salt water was added to allow the "fossil" to dry, then remove it from the container.

Tips & Warnings

• Wait for the sponge to dry or set completely before handling. The wax method is faster and the end product is a bit easier to handle, but it does require a heating element and adult supervision. The salt method takes at least 7 days and the resulting product is more fragile, but more closely resembles the actual premineralization process. Which you choose will depend on your resources, time constraints and class goals.

Resources

• All About Fossils

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