Homemade Hair Hygrometers & Instructions

Hair hygrometers can give an accurate reading of humidity levels in the air.

Human hair possesses an exceptional capacity of reacting to humidity. The length of human hair increases when the level of humidity goes up, and contracts when humidity decreases. This astonishing reaction to moisture led scientists to use human hair in creating the hygrometer; a device used for measuring the humidity level in the air. A homemade hygrometer can work efficiently to help you predict the weather or even foresee bad hair days.

Things You'll Need

• Milk carton
• Large sewing needle
• Broom straw, 2 inches long
• Glue
• Penny
• Strand of human hair, 9 inches long
• Paper clip
• 4 thumbtacks
• Circular paper scale

Instructions

1. Empty the milk carton and rinse.

2. Cut a horizontal slit on the top of the milk carton.

3. Insert the paper clip into the slit.

4. Cut an "H" shape near the bottom end of the carton. Make sure you do so on the same side of the carton where you made the top slit.

5. Bend the tabs you created with the "H" shape into an upright position.

6. Pass the sewing needle through the center of each tab. Do not detach.

7. Attach the broom straw to the needle by passing it through its eye. The straw will be the pointer.

8. Attach the strand of hair to the paper clip on the top of the carton and wind it around the needle to reach the other end of the carton.

9. Glue a penny to the unattached end of the hair strand and let it fall on the bottom end of the carton.

10. Place the paper scale beneath the straw using the thumbtacks.

Tips & Warnings

• To calibrate the two extremes on the hygrometer scale, use a hairdryer to dry the hair completely until the straw pointer stops moving, and mark its location as 0%. Place the hygrometer on a wet towel and put a wet sponge on the top for 15 minutes. The new position of the pointer should indicate 100% humidity.

• To allow water to penetrate the hair more effectively, wipe the hair strands with a rubbing-alcohol solution prior to use. This will remove any oils from the hair and make it more sensitive to humidity.

References

• Science Buddies: Free Science Project Ideas, Answers & Tools for Serious Students
• The Franklin Institute: Resources for Science Learning
• ALLSTAR Network: Aeronautics for Learning Laboratory for Science, Technology and Research

Resources

• infoplease: All the knowledge you need