Here is an easy-to-build homemade thermometer that can be built in about one hour using materials available at home.
* A plastic film can.
* A straw.
* A wire. (Do no use iron, it rusts)
* Food colorant or beverage powder (Strawberry flavor is better, I like ‘dulce de fresa’ flavor).
* Glue. (Hot glue works better).
First, Make a hole in the cap, insert the straw in the hole (be sure the straw reach the botton of the film can) and seal it with glue or hot glue.
The cap should be sealed before building the thermometer.
Second, put 1/4 of water in the plastic film can (about half inch of water) and add some colorant.
Third, put the cap. If the water doesn’t rise as shows the photo, you need to seal the cap perfectly.
Make the wire straight and put it inside of the straw.
The thermometer is ready to be calibrated. Calibrating this thermometer is not easy but not impossible. First, put your thermomether floating in water and measure the temperature of the water with another thermometer. Mark the level of the thermometer. The next step is to handle your thermometer in your hands and watch how the level rises. Wait for ten minutes until the water line does not rises anymore and mark it.
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