Saturday Science Experiment: Spies and CSIs

     

Looking for a weekend project? Here are three activities that little spies and detectives can do with regular household items. Write secret messages and reveal them easily- no lemon juice or open flames! Then create a fingerprint database of the members of your household with very little mess.

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Spy project #1: Invisible messages with wax and watercolors

Supplies: scrap paper, white crayons, watercolors, paintbrush, an optional smock

Procedure: On a piece of paper, draw a secret message or picture with the white crayon. To reveal the message, paint over it with watercolor paint. Voila! 

The science: The wax from the crayon creates a barrier that keeps the paint from adhering to that part of the paper. In art this is a method called wax resist. You may have used this technique to create designs on dyed Easter eggs. 

© SBF

Spy project #2: Invisible ink with baking soda and juice

Supplies: scrap paper, baking soda, water, dark colored juice (we used grape), paintbrush, small sponge or cotton swabs, an optional smock

Procedure: Mix up the water and baking soda in a 1:1 ratio. Mine was 2 Tbl water and 2 Tbl baking soda. Mix well, then using a paintbrush, paint your secret message on a paper. Let the paper dry completely. To reveal the secret message, dip a cotton swap or a sponge in the dark colored juice (we used grape, but cranberry would also be a good option) then gently "paint" a generous amount onto your message. It will reappear! Note, this is one of those "self-destructing" messages, once it dries, your message won't be very clear anymore.

The science: There are pigments in the juice called anthocyanins. These give the juice its color and react with the baking soda. Anthocyanins work as a pH indicator, just like a piece of litmus or pH paper. pH is the scale of acids and bases. Since baking soda is a base, the pigments react and change color, hence your message is revealed! A similar pH experiment can be found in my post: "Saturday Science Experiment: Science with Christmas Leftovers" 

©SBF

Crime Scene Investigator Project: Fingerprint database

Supplies: pencil, pencil sharpener, scrap paper, scotch tape, your fingers

©SBF

Procedure: Using a freshly sharpened pencil, color a dark splotch on a piece of scrap paper. Rub your finger on the pencil splotch. Using a piece of tape, "lift" the print off of your finger. Place it on your database sheet. You can create a fingerprint database for the whole household!

The science: As we all know, everyone's fingerprint patterns are different. The skin on the fingertips is ridged, which creates a specific pattern that can be left behind on certain surfaces. There are three main types of fingerprint patterns- loops, whorls and arches. Once you have created your database, you can compare the prints for these patterns. Learn more about these patterns in depth here.

©SBF

Did you try any of these activities? Share your experience by commenting below, or e-mailing me at shareitscience@gmail.com

Are you looking for other easy at-home science projects? Check out my "Saturday Science Experiment" page. You'll also find some great quick science experiments for kids here. Happy Experimenting!