Homemade Dinosaur Fossils

As part of our Dinosaur Week, we made our own fossils.  I wish I could claim this brilliant idea, but Jared thought up this one and did most of it with the boys.

To make your own fossils you will need:

• disposable cups (we used 8)
• scissors
• modeling clay
• dinosaur toys (or other items to make impressions)
• plaster of paris
• water
• disposable stir stick (we used a plastic knife)
• tray or newspaper to protect your work surface

A note on the modeling clay:  We used colored clay and it left pigment on final fossil.  I really like the way it looks, but if that bothers you then stick with white clay.  I read in a few places that play dough might not work because it does not peel off easily once the plaster is set.

For the setup, I cut the disposable cups down so they were only about an inch and a half tall.  I also smashed the clay as evenly as I could into each cup.  Older kids can easily do both steps.  I placed the clay filled cups and dinosaurs on a cookie tray as a nice presentation for the boys.  We did this right after dinner and the boys could see the dinosaurs on the counter before we ate.  They were so excited by the time I gave them the tray.

With less assistance than I expected, the boys made footprints in the clay.  Jared also made one profile print of one of the dinosaur heads.

Jared mixed up a very small amount (maybe half a cup) of plaster of paris.  He added just enough water to make a pourable mixture (make sure you use a disposable stir stick).  After the cups were filled with about a quarter inch of plaster, I gently tapped the cups to remove as many air bubbles as possible.  Make sure you do this step on a heat proof surface as the plaster does heat up quite a bit while it sets.  We left ours on the cookie tray.  The plaster sets up pretty quickly, but I let the tray sit overnight just to be sure.

The next morning, I removed the fossils and clay from the cups.  I had to cut the sides of the cup off first to prevent the clay from pulling off the plaster.  Bebop could probably have remove the cups himself, but I knew it would be too hard for Magoo. After lunch we pealed the clay off to reveal the fossils.  I was surprised how easily the clay pulled off, and the detail of the fossil.  The original footprints were still clear in the clay, as Magoo is pointing to in the top, right picture.  The boys had fun trying to match the two halves together after all the fossils were revealed.  We did have a small amount of plaster dust fall off, so again cover your work area.

Originally I planned to put magnets on the back, and may still do that at some point.  We’ve kept these in the school room and the boys both like to play with them.  Magoo will point to them and roar.  I think he has dinosaurs figured out!

This turned out to be much easier than I expected.  We will probably make other impressions in the future.  I definitely want to make footprints after Doodad is born.  I would love to see your projects, so leave a link below if you make something!