Capillary Hygrometer

(English version below)

The capillary hygrometer measures ambient humidity using hair, as it lengthens with humidity! The hair is attached to the top of the cardboard and to the arrow; the arrow will descend if the humidity increases. This can predict rainy weather if the humidity is high, or fair weather if the air is dry.

I got the idea for this experiment from a French children's magazine (Youpi Doc) which used a straw for this construction.

Note: This is an educational project for children; it does not allow for precise measurement.

Materials needed:

• Collect 3 hairs of 25 cm (blonde hair has a greater effect on humidity)
• A cardboard of approximately 20x28 cm
• The printed arrow
• A toothpick
• Tape (or a bit of strong glue)
• Precision pliers are recommended
   

Instructions:

• Take a cardboard of approximately 20x28 cm and place it in portrait mode.
• Position the printed arrow 24 cm from the top of the cardboard.
• Make a hole with the toothpick to fix the arrow about 1 cm from the edge. Caution: Make sure the arrow can turn freely around the toothpick! (Sand the toothpick with sandpaper if necessary.)
• Here comes the tricky part: Glue the end of 3 hairs to the flat part of the arrow with a piece of tape or a dab of glue (or both).
• Keep the arrow horizontal, slightly stretch the hairs by sliding your finger, and glue the other end to the top of the cardboard with tape.
   

The construction is complete!

To test the hygrometer, wet your finger and run it along the length of the hairs; you will see the arrow descend!

You can add markers and decorate the cardboard as you like with markers.

English Version: