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4 inch precision Hair Hygrometer |
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Salem Clock Shop - 1085 Broadway Street NE, Salem, OR 97301 - (503) 581-3803 Fax: (503) 581-3331 |
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You can build a homemade hair hygrometer and use it to help make accurate local weather forecasts. |
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Hair Hygrometer |
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Bill of Materials
· Empty milk carton · Large sewing needle or stiff, thin wire · 2” broom straw · Glue or Scotch/masking tape · Penny · Thumbtacks or small nails · paper or card with scale · Paperclip · 9” strands of straight hair |
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Human hair is astonishingly reactive to moisture. It is used in expensive commercially-made hygrometers with large humidity scales. Therefore, with a little ingenuity, it’s possible to build a homemade hygrometer that is quite accurate. If the need for one had been seen, a hair hygrometer could have been built during the pre-Stone Age and anytime thereafter. Lore has it that long, straight blond hair works best, but if you’re in the middle of China as you read this, local hair will of course, do adequately. |
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Rinse out an empty quart milk carton and lay it on its side. Cut a tiny slit at the top end of the carton for the paperclip and insert it to 2/3rds of its length.
Cut an “H” shape into the top of the carton at the bottom end. When deciding on the height and width of the “H”, remember that the tabs it will create will be used as supports for the pointer spindle. |
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Completed Homemade Hair Hygrometer |
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Bend up the tabs you have created, and if they are much taller than need be, trim them with scissors as we have done in the construction of ours.
Locate the center of the tabs and punch holes for the pointer spindle.
Trim the paper or card (with or without a scale already in place), so that it can be centered beneath the pointer spindle.
Tack it or tape it in place on the carton. We have done both, bending the paper back under the box and Scotch taping it.
Force the broom straw through the eye of the needle, if you are using one. Otherwise, attach the straw to the end of the spindle wire with Barge cement (or something comparable) as we have done.
Glue or tape one end of the hair to the penny. Use the other end to take 3 or 4 turns around the pointer spindle and then tie it to the paperclip, leaving the penny hanging about halfway down the box.
(NOTE: we’ve used black thread instead of hair for better visibility in the photo)
Setting The Hygrometer
Simplest way: take it into the bathroom when you shower. At the end of the shower, set the pointer on the mark furthest to the right...this represents 100% humidity. Hit it with a hair dryer and you should see the needle slide to the left.
Other way: Set the unit on top of a wet hand or bath towel in a sink or dishpan. Cover with a wet dishtowel and let it sit for 20 minutes. Then proceed as above to set the pointer.
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