How to Make Your Own Thermometer

While this thermometer won't tell you if you have a fever or not, it can tell you how hot and cold your surroundings are -- you could even calibrate your thermometer or work out your own scale if you wanted! With just a few basic materials, you can start finding out the temperature of pretty much everything. See Step 1 below to get started.


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    Fill up a graduated cylinder about 1/4 full with tap water and rubbing alcohol. If you don't have a cylinder, find some clear container that's as narrow as possible. But anything from a soda bottle to a mason jar can work -- it's just a matter of how fast your thermometer starts working. The narrower it is, the faster it'll be.
    • When your jar is narrower, the liquid is forced to move more quickly -- it's why all the real thermometers you see are thin and narrow.
    • Don't have rubbing alcohol? Just water works too, but rubbing alcohol expands quicker (forcing movement) and water obviously doesn't move when it's frozen! Anything below 32 degrees Fahrenheit (0 degrees Celsius) can't be recorded.
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    Add in food coloring of your choice to the mixture. Red will mimic mercury, making your thermometer seem more like a thermometer and less like a straw placed in liquid. But why aren't there blue thermometers anyway? Maybe there should be....
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    Insert a straw into the container. It is recommended that you use a clear straw so you can see the liquid rise. If you'd like, put a drop of oil into the placed straw -- the oil will sit on top, preventing any water from evaporating.
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    Cover the top of your container with modeling clay. If it has a lid (like a soda bottle or mason jar), poke a hole into it just big enough so the straw can slide through; you want as few air holes to cover up as possible. Then, grab your clay and create an air-tight seal, molding it around the top of your container or hole you made for your straw. If any air can get in, it'll warp your findings.
    • Play-dough works, too, as does candle wax or petroleum jelly.
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    Start finding temperatures! Begin by leaving your completed thermometer alone. Where does the water sit when it's just at room temperature. Then, hold the bottle with both hands to make the mixture heat up. What does the water do now?
    • Place your thermometer in different places. In the sunlight, in the fridge, in the closet, on the windowsill. What is happening to the colored liquid?
    • Do note that this can take a bit of time, especially if you're dealing with a wide container or straw. Changes are harder to see when you're dealing with more area.
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    Watch the mixture rise and fall in the straw. In hotter temperatures, liquids expand. This forces the liquid up the straw, mimicking the mercury effect in thermometers. In colder temperatures, it contracts. So where's the hottest point in your school or home? What's the hottest point of the day?
    • Try calibrating your thermometer! Write down where the levels are for different spots around your home or school. Can you roughly figure out what levels correspond to what temperatures? Or do you want to make a new scale all your own? Fahrenheit and Celsius are overused, anyway. You have your own thermometer - might as well start using your own scale!


  • Use a real thermometer to find out what temperatures your thermometer levels correspond to.
  • Write dashes on the side to correspond to different things: days of the weeks, positions around the school, etc.
  • If you go to deconstruct your thermometer, make sure no one drinks out of your container ever again! Definitely put it in the recycling.


  • Make sure you do not squeeze the bottle or straw because the mixture will squirt out. It will make a mess and it stains clothes.
  • Do not drink the mixture. It is not safe for consumption.

Things You'll Need

  • Tap water
  • Rubbing alcohol
  • Graduated cylinder or other clear container
  • Food coloring
  • Straw (it's best to use a thick non-bendable straw)
  • Pen and paper (for recording)
  • Marker (for marking sides of container)

Article Info

Categories: Science for Kids