Storm Glass Specifics

I've been getting questions and comments about the storm glass instructions, mainly pertaining to the chemicals, but also about sealing the container. Here's an email that pretty much covers everything:

Dear Dr. Helmenstine:

I came across your article in which you discuss and describe the use, and, making of, "Fitzroy's Storm Glass". I am interested in making some of these storm glasses for youngsters, however, I am a little confused by the chemical ingredients which are needed to make the camphorized, weather predicting solution contained in the glass vial.

For example, you list one of the ingredients as "ethanol", ... but, what proof is needed? .... or, doesn't proof matter? Can Vodka be used as a substitute for the ethanol / distilled water? Where can pure grain alcohol and pure camphor be bought? I used to by blocks of camphor in drugstores, but, that was many years ago. Can you suggest some suppliers? Are there any alternative chemicals one can use to get the same results?

Any help in locating these chemicals would be greatly appreciated.

Also, does the size of the glass cylinder containing this solution have any bearing on how well this weather/storm glass works? I would like to make some in various diameters, and was wondering if size does matter. How do you suggest that I seal the glass tubes to prevent leakage, or evaporation of the solution? I was thinking maybe some wax, or, epoxy, for a watertight seal. Any thoughts?

Hope you can give me some more detailed information regarding the listed chemicals.

Cordially yours,

Frank

Making these glasses is art as much as science, since the results depend on the chemicals you can find and the container you have available. Here's a little more information that may help those of you with similar questions.

• The proof of the ethanol listed in the recipe is for pure ethanol or 200 proof ethanol.

• Since the project calls for both ethanol and water, you should be able to substitute a lower proof alcohol. You'll add more of this alcohol and less of the water. You do not want denatured alcohol. If you are trying food-grade alcohol, go for the highest possible proof and purity. I'd try everclear before I'd try vodka.

• Ethanol is a type of alcohol, but not all alcohol is ethanol. The project may not work using methanol or isopropyl alcohol.

• I suspect the way you seal the container may have a significant effect on your results. I would use a glass tube and then heat the glass above the solution with a flame to seal the tube. The volume inside the tube would then be constant, except for minor fluctuations as the glass itself expanded/contracted in response to temperature. Sealing the tube with a stopper also works. I do not know if sealing the tube with parafilm, paraffin, or epoxy would work as well. Epoxy evolves gases as it cures. Parafilm is flexible, so the volume inside the container possibly would change in response to temperature.

• Interactions between the solution and the container may play a part in the functioning of the storm glass. I'd use a borosilicate glass, such as pyrex or kimax. I'd use a tube or a globe over another shape. The volume of air sealed into the container could be expected to affect your results. I'm hesitant to make a recommendation regarding how much/little air you want. If you are using a cork or stopper, you can play around with this.

• It's hard to recommend a chemical supplier since who you can use depends on your country of origin. I have a list of suppliers who sell to the general public. You may want to talk to a local science teacher or professor to see if they can order the chemicals for you, since that can greatly simplify things.