MAKE YOUR OWN BAROMETER I
Tightly cover the top of the coffee can with plastic wrap, using a rubber band to hold the plastic wrap in place.
The cover should be tight making the can airtight.
Place the straw horizontally or sideways on the plastic wrap so that two-thirds of the straw is on the can.
Tape the straw to the middle of the plastic wrap so that it will not fall off.
Tape an index card to the can behind the straw. The straw will act as a pointer on the card.
Carefully record the location of the straw on the index card with a pencil. If desired, marks can be drawn on the index card to make observing the changes easier.
After 15 minutes, record the new location of the straw on the index card. Continue checking and recording the straw location as often as you want.
High pressure will make the plastic cave in and the straw go up. Low pressure will make the plastic puff up and the straw go down. If possible, check your measurements with a real barometer.