Homemade Thermometer

With a working barometer in place on our counter, we decided the next weather tool we needed was a thermometer. We actually have several mercury filled thermometers around the house, but we decided to see if we could make our own, kid friendly version.

To begin with we followed instructions, like these from TLC, where the idea was to take a narrow necked bottle, fill it halfway with colored water, stick a straw midway into the water, and seal the neck of the bottle, around the straw, with modeling clay. The idea is the air in the bottle will expand as it heats, pushing the water up the straw, where it can be recorded on a scale, attached behind the straw.

It sounded pretty simple, but we couldn't get it to work. We tried, as some other sites suggested, replacing part, or all, of the water with rubbing alcohol. And we, tried adding a wire, or in our case, a thin crochet hook, into the straw, to break the surface tension of the water. But, we could not get the water to rise in the straw.

Finally, I saw instructions on Homemade Style, using a film canister, where they had punched a hole through the lid for the straw, and then sealed it with hot glue. They stated if the water didn't rise, it was because of an air leak. We decided, that was our problem with the clay.

The only narrow necked bottle I had on hand, was a candy sprinkle bottle, but it did have a lid. The Man of the House was sweet enough to drill a straw sized hole in it for us, while I fired up the glue gun.


It took a lot of glue, but suddenly the water in the straw rose up above the lid, and held steady. It was a very exciting moment.


We marked room temperature on the piece of cardboard, we'd taped to the straw, and then stuck the bottle into a bowl of very hot water. Happily, it didn't melt our bottle, and we were able to watch the water level rise in the straw, to mark the higher temperature.


Then, we stuck our thermometer in a bowl of ice water, and watched the temperature come, very slowly, down.


It's a long way from perfect. We're still having some problems with air leaking, and haven't been able to keep it steady, yet. But, even so, we (okay mainly I) definitely had one of those Tom Hanks, Castaway kind of moments, when we sat the thermometer in the hot water, and the colored water started to rise - "I have made a thermometer!" But then, our device might be considered a thermoscope, I'm really not entirely sure.

It's great to be a homeschooler.