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How to Fill a Barometer

Barometers can be used to fairly accurately predict the future weather. When the relative barometric pressure increases, the next day is likely to be sunny and calm. When the relative pressure decreases, the next day is likely to bring winds and stormy weather. There are several different kinds of barometers and some, like the aneroid barometer, don't use liquid. Of those that do use liquid the safest kind use water.

Things You'll Need

2 pans deep enough to submerge your barometer
Water
Food coloring

Instructions

Filling
- 1
  Identify the port of your barometer. Depending on the type of barometer it could be at the top or at the bottom but is most likely on the spout at the side.
- 2
  Prepare two pans: one of cold water and the other of hot water.
- 3
  Submerge the barometer in the hot water to fill it. When air stops bubbling out, plug the port with a finger, transfer to the cold water pan and submerge the barometer port before removing your finger.
- 4
  Repeat filling with hot and then cold water until the water level in the barometer has sufficiently passed the spout hole that the air won't escape during low-pressure days. This distance will vary with the shape of your barometer and the air pressure on the day you fill the barometer.
- 5
  Pour out half the liquid in the spout by upending the barometer after it has equalized to room temperature then return it to the upright position.
- 6
  Add a few drops of food coloring.

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