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.
- Time: 2 hours (including 1 hour of waiting time)
- Cost: $40 (Chemicals are difficult to acquire in small doses, so you’ll be able to make many storm glasses.)
- Difficulty: moderate
- 1 (50-100-milliliter) glass bottle
- 50 milliliters of denatured alcohol (methylated spirit)
- 2.5 grams of potassium nitrate
- 2.5 grams of ammonium chloride
- 25 milliliters of de-ionized water
- 7 grams of camphor powder or crystals
- Cheap water filter
- Measuring cylinder
- Gram scale
- Small containers for measured chemicals
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.
- Note: In the U.S., you may be able to get clear denatured alcohol, and if so, you may skip this step. Make sure, though, that the spirit you get is ethanol.
- Warning: Do not use this filter for drinking water when you’re done. You may, however, save it to filter more ethanol in the future.
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.
- Note: If you live in a warmer climate than the U.K., increase the amount of ammonium chloride and potassium nitrate you use. Simply put, you can dissolve more chemicals in warmer water, so you’ll need to ensure you’ve got enough in your mixture for crystals to form.
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:
- Too cloudy or with some froth at the top: Add more ethanol, a few milliliters at a time.
- Too clear: Add more camphor.
- No sharp crystals: Add more ammonium chloride and potassium nitrate.
- Grains at the bottom: Add more water. Do so a few milliliters at a time.
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.