What is a Storm Glass? How does it Work? All you need to Know

Since ancient times, people have tried to map out atmospheric patterns to predict the upcoming changes in the weather. However, formal weather forecasting has been popularized only since the 19th century. 

Early warnings of incoming storms will be quite helpful in taking precautionary steps to protect human life and properties as much as possible. Weather forecasting is also of utmost importance to farmers and agriculturists as it enables them to devise proper plans and strategies.

what is a storm glass

The aviation industry also needs to be aware of any turbulence or storms to minimize risks. The military also benefits from weather forecasting.

As technology has developed, the methods, techniques, and equipment used to predict the weather have evolved. There is a shortage of devices to help track weather patterns.

Let’s look into an old tool named storm glass that helps in alerting oncoming storms without needing physical exertion. You can find out about a storm from where you are, without moving.

What is a Storm glass?

An instrument that can intimate a change in weather patterns by transformations in its crystalline form is called storm glass.

The changes in weather lead to changes in chemical reactions. This is the fundamental principle based on which the storm glass works. It is believed that crystals grow inside these glasses due to temperature variation.

History of Weather Predicting Storm Glass

Though these devices have been in use since the 18th century in France, who developed it remains a mystery. These storm glasses were popularised by Robert Fitzroy, who captained the HMS Beagle during Charles Darwin’s journey.

He was the resident meteorologist and hydrologist who used several chronometers and barometers to aid weather forecasting. Fitzroy used storm glasses as a barometer to observe weather changes, which is why they are called Fitzroy barometers. They are also referred to as storm globe, storm glass barometer, weather glass globe, and glass weather station.

He published a book called “The Weather Book” in which he described the properties and function of the glasses. However, he was clear about the fact that these glasses were used in France and England, decades before his book.

He opined that the glasses functioned differently based on how the glasses were created or produced. The glass shouldn’t be open to the external environment, according to Fitzroy, and should be sealed hermetically.

The camphor must be dissolved partially in alcohol or water, leaving some amount of air space. The British crown supplied fishers with these Fitzroy Barometers for predicting more storms when harsh weather hit the British Isles.

Principle of a Storm Glass

In a storm glass, weather changes are predicted using crystallization in a completely sealed container with a mixture of water and ethanol on exposure to different temperatures.

The sealed container is filled with a colorless and transparent liquid that undergoes the crystallization or cloud creation or formation of other structures. The liquid must be free of any impurities to prevent the formation of a colored liquid instead.

The liquid composition varies; however, it is usually composed of camphor, nitrate potassium, dissolved in alcohol and water with an air passage. The extent of crystallization indicates the threat of storms.

Working of a Storm Glass

In barometers, the liquid level usually increases or decreases in the tube according to atmospheric pressure. However, sealed glasses aren’t exposed to the pressure variations required for crystallization.

The surface interactions between the clear liquid and the sealed container's glass wall can cause crystallization.

A supersaturated solution is formed at higher temperature levels, due to which there is the complete dissolution of a solute in the solvent.

The basic principle upon which a storm glass works is that changes in temperature and pressure directly affect the solubility, leading to crystal formation.

Where to Place a Storm Glass?

Storm glasses are not particularly outdoor-use devices, so make sure they are placed away from direct sunlight, wind, or rain.

As they shouldn’t be exposed to sudden changes in temperature and pressure, it is advisable not to keep it near an open window, and better placed near a stand or table at the corners of the house far from windows or near your sofa or bedside tables.

Make sure it is placed in an interior location away from wind and sun rays.

How to Reset a Storm Glass?

After heavy usage, in case your glass starts acting funny, forming awkward crystallizations, or if the liquid is cloudy and unclear without the formation of crystals, you need to recalibrate your device.

Resetting a storm glass is quite easy. You just need to warm the mixture in a sealed container. You can use a hairdryer and blow it on the glass for warming- don’t heat the glass.

Blow the glass till the liquid is at room temperature. Gently move the glass while blowing to ensure that crystals return to their standard molecular orientations. If the liquid inside turns clear, your glass has been successfully reset

How to Read a Storm Glass?

The liquid inside the storm glass is affected by temperature variations and can depict changes in the atmosphere.

Here are the factors to consider while interpreting a storm glass:

  • If the liquid inside the sealed container is clear, it means the weather will be bright and sunny with no extreme changes.
  • If small dots form on the liquid's surface, it indicates that there might be humid or foggy environments.
  • If the liquid turns cloudy along with the presence of small stars on the surface, it may mean either thunderstorms or snow, based on the temperature and season.
  • If many large flakes are scattered throughout the liquid, it represents rain or snow, with overcast skies.
  • If a thread like structures is present at the top of the vessel, it shows windy gales are ahead.
  • In case crystals are formed at the bottom, frosts are likely to occur.

How to Make a Storm Glass?

Storm glasses are niche units that you can as a decorative piece in your house, which serves a function. You can make a storm glass yourself by following the below mentioned steps.

First you need to collect the following materials to make a storm glass.

  • 2.5g potassium nitrate
  • 2.5g ammonium chloride
  • 33ml distilled water
  • 40ml ethanol
  • 10g camphor (natural camphor)
  • 2 beakers for mixing
  • A completely sealable glass container

After collecting the required materials, follow the below-mentioned steps.


Step 1 - Dissolve required solvents

In a beaker, dissolve both nitrate and ammonium chloride.


Step 2 - Dissolve secondary solvents

Let camphor and ethanol dissolve in another beaker.


Step 3 - Mix contents

Add the contents of the first beaker into the second and mix gently.


Step 4 - Let the mixture dissolve completely

Place the second beaker with all the components in some warm water for mixing completely. The storm glass tube should be decanted and sealed.


Step 5 - Heat the mixture

Place the mixture in a corked test tube as well and heat the top of the tube until it becomes soft and the edges melt completely. Wrap the cork with paraffin or wax coating for proper sealing.

Thats all your storm glass is ready now. It is one of the most fun, simple, easy, and convenient methods of weather prediction. Nowadays, it is also used as a decorative piece and relaxation or soothing tool. They make great gifts as well.

They are one of the oldest methods used for weather forecasting, and as such, it is rudimentary and not fair to judge the accuracy of the device. But, these glasses do provide you with accurate results and storm warnings many times.


Nowadays, these storm glasses are subjects of fascination and objects of curiosity among people. The method and procedure of creating the glasses are an art more than science, affecting the accuracy. 

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About the Author


I am Tim, a weather enthusiast who loves to watch hurricanes and all other harsh weather conditions. I studied B.Sc(Meteorology) at the University of Miami. With excellent knowledge of Weather Forecasting, Meteorology, and Environmental Science, I am currently working in San Francisco as a Meteorologist. Also, I am a member of The Weather Channel and AccuWeather. In this blog, I will write a detailed review of Weather instruments that you need for survival and other activities.