Storm Glass: Functioning of the Crystal Barometer

Weather enthusiasts or science hobbyists may have heard of the crystal barometer, also known as the storm glass or the Weather Predicting Storm Glass. This article takes a closer look at this weather forecasting device, discussing its history and working principle.

Origin of Fitzroy's Barometer

For some reason, the true inventor of the storm glass is unknown. What we do know, however, is that a British naval officer by the name of Admiral Robert FitzRoy is the man responsible for its fame.


Admiral FitzRoy was passionate about the weather and, during his stay aboard the HMS Beagle, he conducted numerous experiments with the storm glass and meticulously documented all his findings.

FitzRoy fervently advocated the use of storm glass throughout the UK to help meteorologists make better weather forecasts, especially after a storm in 1859 caused hundreds of deaths at sea.

Given that the most accurate barometers of the time were too expensive for mass production, the British Crown ordered a large number of storm glasses to be distributed to coastal towns and maritime communities in the British Isles.

At that time, storm glasses became commonly known as "FitzRoy Barometers."

What is a Crystal Barometer?

Fitzroy's barometer, also known as the crystal barometer or storm glass, is a tool used to measure atmospheric pressure and predict upcoming weather conditions.


It consists of a glass tube containing a mixture of chemicals in purified water that crystallizes in a way that can predict the weather several days in advance, typically one to three days.

The most common ingredients inside these devices include ethanol, distilled water, ammonium chloride, potassium nitrate, and camphor, although different storm glasses may have different combinations of these ingredients.

How Does the Crystal Barometer Work?

The crystal barometer is a very simple tool to use. Just place it in a spot with little wind and watch the formation of crystals form or not in the tube. According to the appearance of the liquid, it gives an indication of the atmospheric pressure, and therefore, the upcoming weather.


Here is how to read a crystal barometer:

  • Clear liquid: Sunny and pleasant conditions
  • Small flakes in clear liquid during clear winter days: Snowy conditions expected
  • Large flakes distributed in the liquid: Cloudy and damp conditions in temperate climates; snowy conditions in winter
  • Threads near the top of the liquid: Windy conditions expected
  • Cloudy liquid: Cloudy weather with a chance of rain
  • Cloudy liquid with small flakes: Storms and precipitation expected
  • Small dots appear in the liquid: Damp or foggy weather expected
  • Crystals appear at the bottom of the liquid: Freezing conditions expected

Is a Storm Glass Accurate?

Our opinion is that storm glasses should not be considered a legitimate meteorological instrument, but rather a scientific decorative object and a conversation starter for your desk or coffee table.

If you are looking for accurate weather forecasts for your area, invest in a home weather station instead. Most home weather stations use barometric pressure to forecast weather conditions, and over time, barometric pressure has proven to be a much more accurate forecasting method.

If you're looking for a functional and decorative meteorological instrument that's reasonably accurate, we recommend a Galileo thermometer.

Our Opinion on the Weather Predicting Storm Glass

When looking to buy a Storm Glass, remember that it's more of a coffee table ornament than a genuine weather forecasting tool. However, if you keep this in mind and are a weather enthusiast (or know someone who is), a storm glass will make an excellent conversation starter or a great scientific gift for a loved one.

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