Making Fossils

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Mining and Resources, Rocks, Soil and Erosion

Alternative titles: Plaster Fossil Casting

Summary

Students create fossil replicas by pressing shells, leaves, or other objects into plasticine to form a mold, then filling it with plaster of paris. The plaster hardens into a fossil-like cast that can be painted for detail.

Procedure

Prepare a workspace covered with newspaper.
Press a shell, leaf, pine cone, or small object into a piece of plasticine to create an impression.
Mix plaster of paris in a disposable tub until smooth and fairly thick.
Pour the plaster into the plasticine mold, covering the impression.
Allow the plaster to dry completely.
Remove the hardened plaster cast from the plasticine to reveal the fossil replica.
Optionally, paint the dried plaster fossil with acrylic paints to highlight details.

Links

How to make a fossil with Plaster of Paris - Milni:

Make a Dinosaur Fossil - Nanogirl's Great Science Adventures - Dr Michelle Dickinson:

📄 Making Fossils - preproom.org: https://www.preproom.org/practicals/pr.aspx?prID=1048

Variations

Use small toy dinosaurs or animal figures for fun fossil impressions.
Experiment with different plant types (thick leaves, pine needles, flowers) to compare fossil detail.
Create a “fossil dig” activity by burying finished plaster fossils in sand for students to excavate.

Safety Precautions

Wear gloves when handling plaster of paris.
Wear safety glasses to protect against splashes.
Do not pour leftover plaster down sinks; allow it to harden and dispose of it in the trash.
Work in a well-ventilated area and avoid inhaling plaster dust.

Questions to Consider

How does plaster of paris represent natural sediment in fossil formation? (It hardens around the object just like sediments solidify into rock.)
Why do shells and sturdy leaves make better fossils than thin or flat objects? (They create clearer, deeper impressions.)
What differences might you see between natural fossils and your plaster fossils? (Natural fossils may contain mineral replacement, fine details, or be part of layered rock.)
Why are fossils important to scientists? (They provide evidence of past life, environments, and evolution.)