Make a Hygrometer to Measure Humidity

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

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)