Have you ever been hiking and come across a really cool animal track? Maybe you don’t know what animal made it, or maybe you do know, but the track is just so perfect that you wish you could bundle it up and take it home to admire? Maybe you’ve got a kid who loves animals and nature, who could use a little hands-on science enrichment?
You need to know how to field cast.
Field casting is easy, requiring just plaster of Paris, used cardboard food packaging, masking tape, and water. It won’t take a ton of time away from your hike, and it’ll leave you with a great memory and a useful piece of scientific evidence for studying the real animals who’ve walked your path.
1. Find an animal track. We’ve chosen to hike in the woods behind our house the day after a big rainfall, and my ten-year-old finds just what we’d expect to find: deer tracks!
2. Make a cardboard collar around the track. Cut strips of the cardboard food packaging about 1″ wide and long enough to completely encircle the track; tape pieces together with masking tape to lengthen them if necessary.
Tape the two ends together into a collar that will circle the track.
3. Mix the plaster of Paris. Although there are specific ratios of plaster to water that will guarantee a standard result (and I used to do all our field casting that way), I went on a dino dig earlier this summer and learned there how to simply eyeball my plaster mixture. In a throwaway plastic cup that’s at the end of its life, dump some dry plaster, then add some water and stir with a stick. You’re looking for a pudding consistency, better thin than thick, so continue to gradually add plaster or water to reach this approximate consistency.
4. Pour into the animal track. We always need two people for this, one person to steady the collar and one person to actually pour.
The thinner the consistency of the plaster of Paris is, the better it will fill the animal track without bubbles, but the longer it will take to cure–use your own judgment about how much free time you have to kill making field casts on your hike.
5. Remove the cast. When the plaster is firm to the touch, you can remove the cast and clean up your work.
The field cast will be dirty, but you can rinse it, and then label or paint it.
If you’d like to hang the field cast on your wall later (we do this sometimes), unbend a paperclip into a hook, then embed it in the plaster after you’ve poured it.
If you’ve got an extra-savvy kid who needs a science fair project, have them see what information they can learn about an animal based solely on its track. Height? Weight? Age?
This is also a great technique to employ if you happen to come across an animal track that you can’t identify. You might come up with the first conclusive evidence of the elusive Sasquatch, or the wily chupacabra!
Actually… I have a story about the chupacabra. Buy me a margarita sometime, and I’ll tell you all about it.