Plaster “Fossil” Casts


  • Students will observe and discuss the cause/effect relationship between the natural forces (weathering, erosion, heat, & pressure) and rocks
  • By investigating the everyday uses of rocks and minerals, students will explain how their properties determine how they are used (e.g. toothpaste, sandpaper, vitamins, granite foundations)
  • Science Safety- – Students will follow safety instructions, directions, and use appropriate safety equipment.

Students get to make their own plaster casts, to explore how seabed, decay, and falling sediment work together to make fossils. This project is best done with 2-3 students at a time, cycling between other classroom work. Students get a paper cup with a ball of clay in it. They press the ball of clay to cover the bottom of the cup. Then, they choose a plastic bug or animal to press into the clay to make the impression. Lastly, an adult measures water into individual cups of plaster and the students must mix the plaster thoroughly and then pour it into the mold. The casts need to be left overnight to dry completely, then the paper cup can be cut and torn away from the mold and cast, the cast can be removed, and the mold clay can be stored and reused later.


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