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Lately I've been discussing about the temperature inside a shed with a friend. Due we had no thermometer, we couldn't check our intentions.

So how could we improvise a thermometer next time? We can use anything you can find in general households.

  • Plot twist: you can find a thermometer in a general household. lol – Sempie Jun 29 '15 at 12:28
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There's a pretty simple way to build your own thermometer with household items. Though it can only show temperature changes. If you really want to know how much degrees the temperature changes you'll need to calibrate your self-made thermometer with a real thermometer.

Simple explanation:ref

Here's a video in case you prefer explanations with an example

What You Need:

  • Water
  • Rubbing alcohol
  • 11-ounce clear, narrow-necked plastic bottle
  • Red food coloring
  • Clear plastic drinking straw
  • Modeling clay
  • Store bought thermometer (optional)

What You Do:

  1. Add equal parts tap water and rubbing alcohol to the bottle, filling it about a quarter of the way up.
  2. Add a couple drops of red food coloring and mix by shaking the bottle.
  3. Put the straw in the bottle, making sure it doesn't touch the bottom.
  4. Use the modeling clay to seal the straw in place. Leave a portion of the straw sticking out from the bottle, making sure the clay forms a tight seal around the straw and over the bottle mouth, but don't close off the straw's opening.
  5. To test if the homemade thermometer works, have your child place his hands around the bottle and observe what happens to the mixture.

self-made thermometer

If made as explained above, you will only see temperature rises. To also see falls in temperature you need to add a few drops of your red mixture to the straw.

On wikihow there also are some useful tips:

  • add a drop of cooking oil to the straw. It will prevent the solution from evaporating and provides a clear line to observe changes.
  • to actually measure temperature changes in degrees you need to add a scale
    1. Add solution to the straw until the level is above the clay (provided your thermometer doesn't look like on the picture above and the straw is actually longer than your bottle (see this image from wikihow)
    2. Fix a piece of paper to the straw using clear tape
    3. use a commercial thermometer to measure the current air temperature, mark this temperature on your just added piece of paper
      • repeat this process with different temperatures

As far as I read through the instructions on the linked sites, this isn't intended for air measuring. I guess, if you don't want to measure small temperature changes this will work for air measurement as well.

  • How much do all these parts cost? The bottle could be repurposed, and water is ubiquitous, but the rest aren't common household items (except maybe the modeling clay if you have young children). Is it really cheaper than buying a thermometer? – Gilles Mar 1 '15 at 15:48
  • @Gilles Rubbing alcohol costs a few bucks and is found in personal care products. Food coloring is also pretty cheap. But if you have to buy all those products a usual simple thermometer may be cheaper to buy. – Alex Mar 1 '15 at 16:00
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You can improvise a thermometer with 4 simple ingredients that can be found in most households:

  • Water Bottle
  • Drinking Straw (clear)
  • Food Colouring
  • Modelling Clay / mold-able adhesive (blue tac)

Now what you can do is put a few drops of food colouring into your water bottle and fill it up to the top with lukewarm water.

Then insert your clear (non-bendy) drinking straw a couple of inches into the top of the bottle and then mold your clay / putty (play-dough would work) around the straw and the top of the bottle until you have an air tight sort of lid with a straw coming out of it. (Be careful not to squash your straw as it needs to be free to pass liquid)

Use a marker to mark on the level of the water in the straw (assuming room temperature). You can then put it in a bowl of hot water and the water in the straw should rise and you can now mark on this temperature.
Similarly with some ice-water, the level of water in the straw should decrease and you can mark this on the straw too - the fact you have no thermometer makes it hard to know exactly what temperature these markings are at but you can know if it is 'ice-water' cold or 'boiling water' hot.

If you set this wherever you need it, you'll have a rough idea of what the temperature is in the room.

Note that water isn't that quick to respond to temperature changes so you can make it a 50/50 solution of rubbing alcohol and water and this should give a slightly quicker response.

This link gives and explanation as to how it all works if you are interested!

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