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How to Know the Humidity Level With a Hair Hygrometer

In the 17th century, scientists became fascinated with ways of measuring the amount of moisture in the air. Horace Benedict de Saussare, a Swiss scientist, remarked that hair responds to humidity levels and incorporated hair into his hygrometer design. Hair makes an ideal substance for this weather instrument because it expands and contracts in response to changing humidity levels. When humidity levels rise, hair lengthens. Conversely, when humidity levels fall, hair shortens.

Things You'll Need

Rubbing alcohol
Water
Cotton swab
3 strands of hair, each at least 8 inches long
Flat piece of thin plastic
Scissors
2 nails or pushpins
Dime
Tape
Glue
Piece of Styrofoam or wood, 4 inches by 10 inches
Hammer
Hair dryer
Pen
Ruler

Instructions

- 1
  Mix two teaspoons of rubbing alcohol with eight teaspoons of water. Dip a cotton swab into the solution and wipe the hair.
- 2
  Cut your plastic into an isosceles triangle with a 1-inch base and a 3-inch height. Good choices for plastic include a cancelled credit card, old library card or a membership card that you no longer use. This piece of plastic will be the pointer on your hygrometer.
- 3
  Stick the nail or pushpin through the center of the base of the pointer, approximately one-quarter inch from the edge. Wiggle the nail around to make the hole slightly bigger. The pointer should move around freely.
- 4
  Tape your dime near the tip of the pointer.
- 5
  Glue one end of all of the hair strands to the pointer, halfway between the dime and the nail or pushpin.
- 6
  Attach the pointer to your Styrofoam or wood, approximately two and a half inches from the bottom, by hammering the nail or pushing the pushpin into the wood or Styrofoam.
- 7
  Attach the other nail or pushpin to the wood or Styrofoam, approximately one inch from the top and directly above the hair on the pointer.
- 8
  Pull the hair strands gently and wrap the free ends around the top nail. Continue wrapping until the hair pulls the pointer to a horizontal position. When the hygrometer is upright, the pointer should be parallel to the ground. Glue the hair to the nail to secure it.
- 9
  Calibrate your hygrometer. Dry the hair with a hair dryer until the pointer stops moving. Mark the pointer̵7;s location on the wood or Styrofoam as 0 percent.
- 10
  Bring your hygrometer into the bathroom and take a shower. At the end of your shower, mark the pointer̵7;s location as 100 percent.
- 11
  Measure the distance between 0 and 100 percent with your ruler. Divide the distance into 10 equal increments to indicate the other percentages, in increments of 10 percent. Mark these measurements with your pen. These percentages represent the humidity levels.

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