If Junior is looking for a fun science experiment involving some dangerous hazardous substances (both of which are readily available on Amazon or at almost any hardware store), then he or she can’t go wrong with this 1924 demonstration of how to make “smoke rings” from the November 1924 issue of Science and Invention.

You start by getting some ammonia (called “ammonia water” in this diagram) and some good ol’ Hydrochloric Acid (also known as muriatic acid). Arrange them in bottles and tubes as shown here. To avoid spillage, you need to make sure the ends of the tubes are level with the level of the liquid in the bottles. The fumes combine in the box to form ammonium chloride, and the tiny crystals form a thick white “smoke”. When you tap on the back of the box, a smoke ring emerges.

Note: These chemicals really are dangerous, so use great caution in carrying out the experiment. In particular, we recommend doing it outside, or in a room with lots of ventilation.

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To take home the blue ribbon in the science fair in a spectacular way, you can’t go wrong with an old-fashioned Tesla coil, and the July 1964 issue of Popular Electronics tells exactly how to make one. The most exotic part you’ll need to track down is a neon sign transformer, but thanks to the internet, you can find one on Amazon.

The capacitor is home made, from sheet metal and a glass dielectric.

The article warns that the voltages used in the project can be lethal. The secondary of the neon transformer is 12,000 volts, and the voltage at the coil can be up to a quarter million volts.

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Students with artistic sensitivities might feel intimidated by the science fair, but they needn’t be. By recreating all or part of this 1944 demonstration, such a student can wow the audience with a ballet performance, demonstrate the principles of refraction of light, and take home the blue ribbon, undoubtedly to the consternation of the science nerds who thought they had no competition.

The original 1944 version was put on by Bausch & Lomb Optical Co. for its employees, to demonstrate the scientific principles used in the bomb sight components the company was making. They put together a ballet-like performance set to music, while the dancers pulled white ribbons through the lenses, demonstrating the path of light.

Of course, this display takes a great deal of preparation. For students who are desperately searching for a project the night before the science fair, try our earlier project demonstrating the same principles, one that can be whipped together the night before.

A complete description, along with more pictures, can be found in the April 17, 1944 issue of Life magazine.

The advanced student looking for a spectacular science fair project can’t go wrong by constructing the 60-cycle repulsion coil resonance engine described in the March 1964 issue of Popular Electronics. Essentially, it’s a coil and capacitor tuned to be resonant at exactly 60 Hz. The cover photo above shows the coil being used to repel a two-inch piece of aluminum tubing.

The device is called an engine because it can be used as shown to the left, with a reciprocating piston driving a flywheel. As with any single piston engine, to get started it requires a spin to get started, unless it happens to be in just the right spot.

The author suggests a number of other experiments that can be done with the device, all of which we guarantee will bring home the blue ribbon.

If Junior is looking for an easy-to-construct science fair project, this one from the January 1939 issue of Popular Science is certain to bring home the blue ribbon. It answers the question of whether gasses can be weighed.

Junior should carefully construct two boxes made of paper, and make them into the balance shown here, so that the slightest weight tips the scale. Then, some invisible gas is poured into one of the boxes, and that side of the scale moves down, demonstrating that the invisible gas is, indeed, heavier than air and can be weighed.

As for the gas to use, the magazine recommends carbon tetracholoride. Of course, that’s dangerous stuff, and would result in the hazmat team shutting down the science fair. Instead, for almost as good a reaction, some carbon dioxide gas can be quickly produced by mixing a little vinegar and baking soda in a tall glass. We showed how to do a similar experiment in an earlier post, and Junior might want to do both.

If Junior has a science fair project that’s due soon, and he or she likes playing with fire, then this simple project form 85 years ago is just the thing to take home the blue ribbon.

Like any good science fair project, this one answers a question, namely, “will a drop of water evaporate faster on a red-hot piece of metal, or on one that is only moderately hot?” The classmates, and probably the teacher, will undoubtedly place their bets on the one that’s red hot, but Junior will prove them wrong.

The reason is that on the red hot surface, a cushion of steam forms, and the drop of water mostly retains its shape as it dances about. But if the surface is only moderately hot, the water spreads out and evaporates immediately.

Most schools have probably turned off the gas to the bunsen burners in the science lab, but you can bring your own from home. You can get this handy propane bunsen burner from Amazon.  In fact, the science teacher will probably be a little bit jealous and want to get one for themself.  The school probably has the lab stand, but if not, you can also get that on Amazon.

This project appeared in the December 1938 issue of Popular Science.

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Today, we have another science fair project suitable for students who like to use dangerous chemicals. It’s a homemade photoelectric cell. It won’t provide large amounts of current, but it is measurable, and it can probably be used to receive a signal from a modulated beam of light, simply by connecting it to an audio amplifier (similar to this previous project).

The cell consists of a beaker of water in which a “pinch” of salt has been added. Into this are inserted strips made of copper and lead. The copper is heated with a torch to oxidize it, after which it is scrubbed with nitric acid. There is some current even in darkness, but when the copper strip is exposed to light, the current increases.

The project appeared in the November 1948 issue of Practical Wireless.