A storm glass is a weather predicting device with crystal formations that supposedly change based on impending weather. However, can this device predict the weather accurately? We wanted to answer the most common questions surrounding storm glasses, and explain why it is likely that they do not work as well as some may claim.
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What Is a Weather Predicting Storm Glass?
Storm glasses contain a mixture of chemicals which are said to crystallize in a way that makes it possible to predict weather conditions several days in advance, typically one to three days.
At the time that storm glasses first appeared (sometime in the 1700s), barometers—a reasonably accurate way to predict the future weather—remained relatively expensive. Most had to rely on cheaper methods of weather prediction, so sometime in the 17th Century an unknown inventor created the storm glass, but we don’t know why or how they did it. They would eventually rise in popularity in the mid-1800s after British Naval Officer Admiral Robert Fitzroy used them aboard the HMS Beagle, which also happened to host a young Charles Darwin doing his initial research on evolution. This is why the storm glass is often called an Admiral Fitzroy Storm Glass.
Admiral Fitzroy was a weather enthusiast, and over the course of his expeditions, he examined the behavior of a storm glass to better understand how it worked. The relationship between the liquid’s behavior and the corresponding weather conditions used today derive from Fitzroy’s work aboard the Beagle.
Fitzroy became so enamored by the storm glass that he pushed for their use throughout the UK to help early meteorologists predict the weather better and more so after an 1859 storm which took many by surprise, resulting in hundreds of deaths at sea.
Storm glasses fell out of favor late in the 19th Century as mercury barometers became more affordable. These days, they have become little more than a conversation piece, rather than weather predictors, and many may not even know that such a device ever existed.
How Does a Storm Glass Work?
Even today we do not entirely understand how these devices work, or how the crystals inside form and change shape. The truth is that there just haven’t been many studies done to figure out the process. 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.
The version of the weather glass used in Fitzroy’s time was not completely sealed (typically by only a rubber cap) so pressure changes may have had some kind of effect. Today’s versions are hermetically sealed, which would likely mean the changes would have something to do with temperature differences outside the glass.
While research is slim on the storm glass (even when they were more commonly used), several studies over the years seem to suggest crystal growth is affected by temperature more than anything.
Is a Storm Glass Accurate?
These same tests also showed to be no better than a 50/50 chance of being correct, essentially leaving the predictions up to chance. Our opinion is that storm glasses should not be relied upon as a legitimate weather instrument but more of a conversation piece for your office or coffee table.
If you’re looking for precise weather forecasts for your local area, invest in a home weather station instead. Most home weather stations use barometric pressure to make predictions on weather conditions, over time barometric pressure has shown to be a much more accurate method of forecasting.
If you’re searching for a functional and decorative weather instrument that is reasonably accurate, we recommend a Galileo thermometer. Learn how to read a Galileo thermometer and how they work in our article.
How to Read a Storm Glass
As we mentioned earlier, Robert Fitzroy popularized the current method to read a storm glass. Below is the chart used by Fitzroy and others to read a storm glass.
Storm Glass Liquid Appearance
Cloudy with small stars
Sunny and fair
Small, isolated stars during winter
Sunny and fair weather followed by snow in 1-2 days
Large, isolated flakes
Cloudy and humid, snow in the winter
Flakes which rise and stay in the upper part of tube
Winds in the atmosphere, changeable weather
Rain or rain soon
Strands forming near the top
Small floating spots
Crystals at the bottom
Does a Storm Glass Work Indoors? Here Is Where You Should Place It
Storm glasses are not intended for outdoor use, so if you purchase one, keep it indoors. They should also not be placed in a window that receives direct sunlight, or somewhere that may experience sudden temperatures changes during the day. Keep it away from walls facing the outside or near heating and cooling ducts.
How to Make a Storm Glass
Most of the chemicals used to produce the liquid inside of a storm glass are potentially hazardous. Inhalation of these chemicals could make you sick, and you should take care when handling any of the chemicals and prevent exposure to bare skin. We recommend that you buy one instead of making it yourself, especially considering many of the required chemicals can be difficult to obtain.
However, if you really want to make one, there is a way to do it. We recommend checking out the video below. You will need 100 proof vodka, camphor, potassium nitrate, and ammonium chloride. If you can obtain these materials, you’ll be able to make one on your own.
Be very careful and follow the video’s safety instructions to prevent any issues from occurring.
The Best Storm Glass to Buy: Weather Predicting Storm Glass Reviews
To help you decide on the best storm glass to buy, we’ve reviewed three separate models on Amazon that we think are worth considering.
1. Best Overall: Eon Concepts LED Teardrop-Shaped Storm Glass
If making your own seems too dangerous, or you can’t obtain the materials necessary, then the best storm glass to buy is the Eon Concepts Storm Glass on Amazon. This teardrop-shaped glass sits on an LED wooden base which has seven different colors to choose from. It has received solid reviews across the board, although, as we’ve mentioned above, don’t expect the predictions to be accurate from any storm glass.
We think the Eon Concepts storm glass is one of the more visually appealing models on the market. Unlike some other models, it is visually appealing enough to sit on your countertop to accent your other décor rather than being the focal point. A small or large version is available—the large version is about eight and a half inches tall by four and a half wide, and the smaller version five and a half tall by about two and a half inches wide.
We’d recommend the larger model for bigger rooms like a family or living room, while the smaller model is better suited for bedrooms.
Whereas the Eon Concepts storm glass design is subtler, the Lily’s Home Storm Glass with Galileo Thermometer makes more of a statement. It combines a storm glass with a Galileo thermometer encased in a wooden holder with a mahogany finish. This model also includes both a clock and a hygrometer on the front face.
At seven inches tall by four and a quarter inches wide, it’s ever so slightly smaller than the large-sized Eon storm glass, and we’d think this would look best in your living room versus your bedroom. It’s also a clock—making it a suitable replacement for a desk clock if you have space for it.
It’s no more expensive than the Eon Concepts storm glass and generally gets good reviews from buyers. However, it’s less subtle design might be a bit much for some who might merely be looking for a traditional storm glass.
If you’re looking for a slightly cheaper version of the Eon Concepts model, Cavallo Mercantile’s storm glass is a good alternative. It lacks the Eon’s LED base, but still gets excellent reviews for its construction and operation.
Like the Eon, the Cavallo Mercantile comes in small and large sizes (roughly the same dimensions as the Eon). However, in both cases, you’ll be able to pick up this model at a lower price.
One way Cavallo Mercantile’s storm glass differs from others is the manufacturer’s choice to use a dark wood base versus the light wood base that is found on many other models. We think this makes the Cavallo Mercantile storm glass stand out more, and might be a better option if you have other dark wood pieces throughout your home.
When you’re looking to buy a weather glass, remember that they are more of a coffee table ornament than an actual weather forecasting tool. However, if you keep this in mind, and are a weather enthusiast (or know somebody who is), a storm glass will be a great conversation piece or gift. For more cool weather-related gift ideas, take a look at our list of the best gifts for weather geeks.