Make a Hygrometer to Measure Humidity

Here's how.

Active Time

20-30 minutes

Total Project Time

45 minutes to 1 hour

Key Concepts

Humidity

https://www.youtube.com/watch?v=NF_nanpcQ9c

Introduction

Does your hair go frizzy during "April showers," when the weather turns damp? Strands of hair can relax and lengthen when the humidity (or the amount of water vapor in the air) increases, and then contract again when the humidity decreases. In fact, the rate of change in the length of hair strands is so dependable that they can actually be used as the basis for a hygrometer, a device that measures the humidity level in the air.

Credits

Sabine De Brabandere, PhD, Science Buddies

This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Next: Materials

Materials

Rubbing alcohol, 70% isopropyl alcohol works well
Measuring spoons
Small bowl
Water
Three long strands of human hair (about 20 centimeters long)
Cotton swab
Drinking straw, preferably a wide, non-bending straw
Scissors
Metric ruler
Glue, fast drying glue or a glue gun work best
Scrap piece of wood, about 25 cm long and 15 cm wide
Two small nails
Hammer
Marker, pencil, or pen
Hair dryer
Ziplock bag, large enough to fit the wood inside and have a little room to spare
Wet sponge or small towel (either paper or cloth)