Hobbies And Interests
Things You'll Need
Instructions
If you want to make a cast of a specific species of dinosaur, you'll need to do a little research online to find an picture of the footprint of the species you're looking for, plus the measurements.
You can approximate a dinosaur footprint and get good detail with a footprint between the size of your hand...about 6" to 8"...up to 12" from back to toe.
However, since most dinosaurs had three toes with claws, like birds' feet, it's fairly easy to trace out a pattern. Look at the pictures throughout this article for some examples.
Once you've found the footprint you want a cast of, make a drawing on paper. If you trace one of a smaller prints, you can take it to a copy shop and have it enlarged to any size you like.
You can also enlarge it yourself by using the grid method: over the original drawing make a grid of 1" squares. On a larger sheet of paper, make a grid of 2" or 3" squares...the same number as on the smaller drawing...depending on how large you want the print to be. To transfer the drawing, copy what is in each grid onto the corresponding grid on the larger paper. Viola...the footprint is now bigger and the proportions remain the same.
Trace your footprint onto cardboard.
Find a place to make your sand mixture for your footprint. Try to stay away from areas that are in full sun; your dirt and plaster mixture may dry out too fast and crack.
If you have a sandbox, that's a great place to work. Lay down garbage bags to contain your sand from the sandbox sand. You can also use the sidewalk or lawn.
If you don't have a place outside, you can mix your sand inside...if you contain the sand in a box of some kind. Line the box with garbage bags to keep any moisture from seeping out onto floors or carpet.
Now to get dirty...this is a great part for kids to help. Mix up sand and water, to a consistency that will hold an imprint. Dinosaurs didn't walk around looking for the right sand to walk in; the footprints that survived are the ones that were made in the right conditions.
Check the mixture by putting your hand in it occasionally. If the imprint stays, and the sand doesn't flow back into the impression, you've got a good mixture.
If the sand cracks and chunks fall into the cast, then it's too dry.
Keep mixing until you can make an imprint that holds its shape.
Once you have your sand mixed, lay your footprint on the sand and press it into the mixture. The bigger your footprint, the deeper into the sand you'll need to press. When you've got a deep enough track, use a sharp stick or knife to make "claw" imprints at the end of the toes.
You can also do some sculpting with paint stirrers or sticks to make a more realistic imprint. Look at your own hand or foot for an ideal of where to make deeper impressions: the pads of your fingers or toes, the outside of your foot, anywhere there would have been lots of pressure.
Place a strip of cardboard a few inches around the footprint, forming a circle to contain the plaster, and push it into the sand. Fasten the ends with a paper clip. If you have a large print, you may need to create the circle with several pieces of paper.
Mix up the plaster of Paris, adding one part water to two parts plaster. Mix to the consistency of pancake batter, with no lumps or air bubbles. You can tap the bottom of the container sharply on the floor several times to get the air out.
Plaster of Paris starts the chemical reaction to harden as soon as it's mixed, so the faster you work the better. Gently pour the plaster into the circle, letting it flow into the footprint. Don't pour directly into the print, as the plaster can distort the track.
When you've got the track and circle of cardboard filled, it's time to let the print harden. Let it sit out of direct sun overnight.
In the morning, remove the cardboard circle and gently lift the cast from the sand. You can gently brush any remaining sand from the track with an old toothbrush or paintbrush. Let the cast continue drying face up.