Don’t ditch your weather app, though.

By Lucy Rogers | Published Nov 22, 2019 10:15 PM

Some “inventions” of the past do not have scientific credibility, but are still delightful to behold. One of those is the storm glass—a sealed clear glass vessel that contains chemicals that crystalize in different ways. People in the mid-1800s believed the shape of the crystals could foretell the weather a couple days in advance: fluffy patterns meant clouds, clear glass meant sunny skies, and snowflake-like crystals meant ice was on its way. I’m not convinced, but I like how they look, so I made myself one. Once you get the ratios right, they are simple to create and great as gifts.

1. Set up your work area. I made my storm glass on the kitchen table. To avoid contamination, I made sure all food products and utensils were put safely away. This is also a good time to remember that you’re going to be working with chemicals, so make sure you read the labels and warnings, especially if you’ve never worked with these before.

2. Prepare the methylated sprit. In the U.K., where I’m based, ethanol is available as methylated spirit—or denatured alcohol—but it contains additives that make it poisonous, bad-tasting, and also purple. Passing the spirit through activated carbon, such as a water filter, removes the purple color, but it will remain poisonous and disgusting. Pour the ethanol into the top of the water filter, and watch as it comes out at the bottom less purple. It will take a few passes to remove all of the color—pour the spirit into another container, then pour it back into the top of the filter. After every couple of passes, flush the filter with water.

3. Measure the liquids into the beakers and the dry chemicals into small containers. I used a few night light candle tins, with the candles removed, of course. You may use whatever you have on hand, but make sure they’re small enough to fit on your scale and large enough to hold about 2 tablespoons of powder. They can be made from any type of solid material. If you need a refresher, all the amounts are above in the list of materials.

4. Create your first mixture (Mixture 1). Pour the potassium nitrate and ammonium chloride into the distilled water. Stir until it is dissolved.

5. Create your second mixture (Mixture 2). Put the camphor into the ethanol and stir until it is dissolved. This may take more than 10 minutes. You may also need to place the beaker in a water bath to heat it—chemicals dissolve better in warmer liquid. I used a kettle to fill a bowl with hot water, then placed my beaker in the hot water.

6. Combine both mixtures together. Slowly add the water mixture (Mixture 1) to the ethanol mixture (Mixture 2) a splash at a time. Stir after each addition. It will go cloudy and then clear again. Keep mixing until it stops changing back and forth, or until you have used all of Mixture 1.

7. Check and correct. Wait for 20 minutes. The liquid may change from clear to cloudy, or crystals may form at the top or bottom of the beaker. Ideally, you’re looking for a clear solution with either fluffy, cloud-like crystals or snowflake-like crystals suspended in it. Depending on the purity of the chemicals you purchased, including the methylated spirit, you may need to try the following, waiting 10-20 minutes between each trial:

8. Pour the mixture into your glass bottle. When you are happy with the mixture, use a funnel and pour it into your bottle. Then seal the lid.

Over the next few days, watch what happens. The contents of the bottle should change between clear, cloudy, and sharp crystals. It may even coincide with the weather outside your window.

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