How to Make an Air Barometer

Measuring barometric pressure is an important part of predicting weather and understanding weather patterns. A simple barometer can be made with things found around the house.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Tape Quart jar Rubber band Scissors Index card with lines Plastic straw Balloon

Making the Barometer

1. Cut off the mouth of the balloon and stretch the remaining part of the balloon tightly over the mouth of the jar.

2. Place the rubber band around the mouth of the jar to anchor the balloon in place. Make sure that the balloon is airtight, so that no air can escape the jar or pass into the jar. The jar must be completely sealed for the barometer to work.

3. Tape one end of the straw to the center of the balloon so that the opposite end hangs over the edge of the jar.

4. Place the jar on a shelf or table next to a wall or some other backdrop, with the straw pointing toward the wall.

5. Tape the index card to the wall or backdrop behind the jar, with the line side facing outward.

6. Check daily to observe and record the position of the straw on the index card. The balloon top will swell or indent depending on whether there is a rise or drop in air pressure. This will cause the straw to move up or down on the index card. If the straw points higher on the index card, there is a rise in pressure, if the straw points lower, there has been a drop in air pressure.

Tips & Warnings

• A barometer can be used both indoors and outdoors. High pressure is usually an indicator of clear weather, while low pressure signals rain and clouds.

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