How to Fill and Read a Glass Barometer

By: Professors Lally & Whittaker

Introduction

barometer 1

Goether Barometer (SOURCE: The Weather Doctor)

Glass weather barometers are used to predict precipitation, humidity, and weather patterns. Glass barometers were first invented and used in the 16th century by Wolfgang von Goethe, a German mathematician.

A weather barometer is also called a “storm glass” or “Goethe Barometer.” The tool works by measuring atmospheric pressure to predict incoming weather. Since the glass is only filled halfway with water, the other half is exposed to the atmosphere. When the outdoor atmospheric pressure rises, the pressure in the glass decreases, and causes the water to move down the spout. Conversely, when pressure decreases outside, pressure in the glass increases, and the water moves up the spout, and often times pours out. Below, you will learn to fill and read a glass barometer (Weather Underground).

 How to Fill the Barometer

What you will need:

  1. 2 large pots or buckets
  2. Weather barometer with hanger
  3. Food coloring

Instructions:

  1. Fill one large pot or bucket with warm-lukewarm water. Fill the second with cold water.
  2. Submerge the entire barometer in the warm water. You will see air bubbles released, causing the water to bubble. Keep the barometer under water until you no longer see air bubbles.
  3. Place one finger over the spout before you pull the barometer out of the water.
  4. Submerge the barometer in cold water while still covering the spout with your finger. Remove your finger, and allow the cold water to fill the barometer until the bubbles stop.
  5. Repeat steps 1-4 until the water settles at about an inch above the spout. Do not forget to seal the spout with your finger each time you move the barometer to a new bucket.
  6. Hang the barometer on its hanger, and allow the water to reach room temperature.
  7. Empty the spout until it is only half full
  8. Add desired food coloring through the spout (Windward Instruments).

 How to Read the Barometer

  1. If the water in the spout falls and moves back into the body of the barometer, this means that outdoor atmospheric pressure has risen. This can indicate a number of weather changes:
    • In the summer, temperatures will rise and clear, sunny skies should be expected.
    • In the winter, temperatures will fall and dry, cold weather will ensue.
    • If the liquid in the tube falls slowly, the weather will stick around. If it drops quickly, then the weather will come and go.
  2. If the water in the spout rises or even spills out of the spout, this means that atmospheric pressure has dropped. This also has many indications.
    • In the summer, a rise in pressure means the temperature will begin to cool, and precipitation should be expected.
    • In the winter, this means that temperatures will rise and, depending on the temperature, snow or rain should be expected.
    • A drop in pressure also indicates a cloudy day. If the water in the barometer rises quickly and greatly, or even spills out, expect heavy and potentially dangerous precipitation (Weather Underground).
barometer2

Atmospheric Pressure Explained (SOURCE: Socratic)

 Conclusion

Once filled and ready to use, the barometer should be kept in a sunlit spot with relatively stagnant temperature. For example, a well-lit bookshelf or table will do. It is not recommended that these barometers be kept on a windowsill because the change in temperature will cause a change in pressure in the glass, causing the water to rise or fall in the spout. If this happens, users could get a false reading (Windward Instruments).

Remember that the pressure is measured relative to the internal pressure of the barometer at the time it was sealed. For this reason, make sure you fill the barometer on a calm, sunny day (Windward Instruments).

 Citations

Barometers for Weather Watching.The Weather Doctor. N.p., n.d. Web. 09 Mar. 2015.

Barometers-How They Work and What They Do.Weather Underground. The Weather Channel, LLC, 21 Apr. 2013. Web. 09 Mar. 2015.

Windward Instruments Water Barometer Instructions.Windward Instruments. Windward Instruments, n.d. Web. 09 Mar. 2015.

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