How to Measure Humidity Using Hair
Weather professionals use sophisticated tools called hygrometers to get precise readings of humidity. However, scientists have used simple hygrometers for well over two centuries. The most popular of these simple hygrometers, a hair hygrometer, has been in use since 1783. These hygrometers operate on the principle that hair expands when wet and contracts when dry. These hygrometers are accurate enough for the average person to use them in tracking humidity at home.
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Things You'll Need
- Wood board
- 2 long nails
- Piece of thin cardboard
- Scissors
- 2 to 3 hair strands
- Hot glue
- Hot glue gun
- Paper
- Pencil
Instructions
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1
Cut a piece of thin cardboard in the shape of an isosceles triangle (a triangle with two equal sides). Push the sharp end of a nail through the center of the wide end of the cardboard triangle. Wiggle it around until the cardboard moves fairly freely but doesn't fall down the shaft of the nail.
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Lay your piece of wood down flat. Hammer the nail with the cardboard triangle on it into the top of the board, about a third of the way in from the left edge and an inch or so from the bottom edge. Position the triangle so that the pointy end--the end opposite the bottom, or unequal side--points straight to the right.
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3
Wash your hair strands thoroughly to remove all the oil on them. Let the strands air dry.
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4
Hot glue one end of your hair strands to the bottom edge of the cardboard triangle, closer to the nail than to the pointy end of the triangle.
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Use your hammer to pound a second nail into the wood board. This nail should be about an inch from the top edge of the board and should be straight up from where you attached the hair strands on the triangle.
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Stretch out your hair strands and hot glue the free ends to the second nail.
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Glue a small piece of paper on the board just to the right of the pointy end of the cardboard triangle. Write DRY on the paper well above the triangle's point and HUMID well below the triangle's point.
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Watch or listen to weather reports over the next few days. Make a mark on the paper wherever the triangle points and write in what the humidity levels were for each mark. This gives you a gauge on your homemade hygrometer. Fill in the gauge when you have a sufficient number of readings from reports. Ideally, your hygrometer should point straight to the right at 50 percent humidity, but the reports will show you where your gauge and hygrometer really sit.
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Monitor the movement of the cardboard triangle every day. As the humidity gets lower, the cardboard triangle will point higher (toward DRY). As the humidity gets higher, the cardboard triangle will move lower (toward HUMID). Write your humidity readings down on a piece of paper to keep a humidity log.
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References
- Photo Credit hair image by Dubravko Grakalic from Fotolia.com
