For the aspiring mad scientist looking for a spectacular science project that combines fire, high voltage, and loud noise, the flame speaker described in the July-August 1968 issue of Elementary Electronics should fit the bill perfectly. We previously written about how a flame can serve as a radio detector. As this article shows, it can also serve as the speaker, as the flame can be induced to emit sound. Depending on how much work you want to do, the quality of the sound can be extremely good. But even a modest investment of time can make the flame produce sound, although the simpler setups will be somewhat distorted.

The general principle is quite simple. The flame constitutes a plasma, often referred to as the fourth state of matter, made up of a cloud of positively charged atoms and free electrons. When an audio frequency signal is applied to the plasma, the positive ions and electrons move, creating a bending of the flame and room-filling sound.

The simplest arrangement is shown here. The output of an audio amplifier is fed to a transformer to step up the voltage. Nearly any transformer can be used. In this case, a bell transformer–ordinarily used to step-down 120 volts to 6 volts–is hooked up in reverse.  Such a transformer can be found inexpensively on Amazon, but it’s probably possible to scavenge one.  A trip to the local thrift store will probably allow you to find a “wall wart” power supply.  If you can find one with an output of about 6 volts ac, then your work is done.  If you can only find one with a DC output, then you’ll need to open it up and remove the rectifier.

The transformer increases the voltage of the audio sufficiently to modulate the flame. This output is connected to two electrodes, in the form or ordinary nails, which are inserted into the flame.

The flame can come from a variety of sources. The higher the temperature the better, but the author was able to produce sound with as little as a single candle. Various types of torches, or even a bunsen burner, can also be used to produce more sound.  An inexpensive butane torch would probably prove most adequate, or you can use an inexpensive propane torch such as the one shown here.

The ordinary combustion products do not provide sufficient plasma, so it is necessary to insert some potassium nitrate into the flame. The article recommends using an asbestos wick, in the form of “asbestos tape used to seal pipe joints in warm-air heating systems.”  If you can’t find the potassium nitrate locally, it’s inexpensive on Amazon.

Of course, asbestos can’t be used today, since it would result in the haz-mat team immediately shutting down the science fair. But the article reveals that the potassium nitrate is in a solution of water, meaning that even a combustible wick would probably survive all but the hottest flames, at least long enough to do the experiment. So it seems that a normal wick, such as used in a kerosene lamp, would be more than adequate. Indeed, with some experimentation, it would seem that almost any kind of fabric could be used, as long as it begins the experiment saturated with water.  Another option would be the use of welding fabric.

More advanced students will want to get rid of the distortion inherent in the simple design, and this can easily be done by providing a bias voltage. The article recommends about 400 volts. Other improvements include replacing the nails with tungsten or nichrome wire, and recommends sources.  You can scavenge the nichrome wire from an old toaster, or buy it inexpensively on Amazon. The article recommends, of course, that proper precautions be taken if the high voltage bias is used. With the original simple setup, however, the experiment should be relatively safe, since no high DC voltages are used.

The original article is available from this link.  Even the simplest version of this experiment is certain to take home a blue ribbon, and the more advanced version could produce truly spectacular results as the flame changes color and pulsates as it produces room-filling sound.  The kid with the potato clock won’t stand a chance.  You can derive some inspiration from this and other videos of flame speakers:

Seventy-five years ago this month, the June 1943 issue of Popular Science showed how to do this seemingly impossible balancing act. The hammer is suspended by a string in the middle, with the end of the handle exerting an upward force on the end of the ruler. Since the center of gravity is under the table, the ruler stays in place.

This simple stunt could be the basis for an elegantly simple science fair project regarding leverage.

If you’re reading this page because Junior just remembered that the science fair project needs to be handed in tomorrow, there’s no need to panic! This site is full of interesting science fair projects.  Some of those projects might take some time to complete, but many of them can be whipped into shape in an evening.  This one falls into that category.  Junior can make an impressive display by mapping magnetic lines of force.

If the project is due tomorrow, have Junior start reading the Wikipedia article about magnetic lines of force.  In the meantime, you can race to the hardware store or dollar store to get the items he’ll need, if you don’t have them already.

First, you’ll need some insulated wire.  Any kind of wire will work, as long as it’s insulated.  At the dollar store, you can probably find it in the electronics aisle in the form of speaker wire.  Get about 10-20 feet.

You’ll also need a battery.  The old-fashioned dry cells shown above look nice, but there’s really no need.  Normal D-cell flashlight batteries will work just fine.  Get a few extras, since they will be used up quickly.

Finally, you’ll need a cheap compass.  If you don’t have one already, you can probably find one in the toy department, and it will work fine.  And while you’re there, don’t forget to get the obligatory poster board, markers, etc.

Have junior construct the loop of wire shown in the picture, and embed it in a piece of cardboard.  Hook the ends of the wire to the battery, and you have created an electromagnet.  Simply move the compass around the cardboard, and with a pencil, make a small mark showing what direction the compass is pointing.  Connect all of these marks, and you will have an accurate diagram of the magnetic lines of force.

The teacher will be impressed, Junior will get a blue ribbon, and nobody will know that he waited until the last minute.

You can find more details in the March 1943 issue of Popular Science, from which the illustration was taken.

I’m not able to make out the text, but this Soviet magazine from November 1967 appears to be right up our alley. It appears to be giving young comrades instructions for building a home blast furnace!

I am able to make out the caption for the item between the vacuum cleaner and the wall outlet, and it’s marked “rheostat.” Presumably, it’s set to blow air into the combustion chamber, and the young Soviet mad scientist can adjust the intensity of the furnace with the rheostat.

The illustration appeared in the November 1957 issue of Юный техник magazine.  A treasure trove of similar magazines, many on the subject of radio, can be found at Журналы СССР.

Contrary to first impression, the logo at the top of the page is Ют, the abbreviation for the name of the magazine. But if it looked like HOT at first glance, we don’t blame you. This contraption will indeed get hot!

We put this item in the “science fair ideas” category. However, we do recommend that before duplicating this project, young scientists should have the article translated to see if it contains any safety warnings. I suspect some might be called for.

With it being unfairly accused of responsibility for many a UFO sighting, the humble substance known as swamp gas today has an undeservedly bad reputation. But this was not the case for this gentleman using swamp gas as part of his scientific inquiry, following the plans set forth in the November 1937 issue of Popular Science, in an article with the title of “Fun With Explosive Gasses.” With a title like that, you can bet that it’s going to appear on these pages.  The article notes that hydrocarbons can be the subject of many spectacular experiments by the amateur chemist, and details a number of explosively good experiments.

The article begins tantalyzingly with some of the possibilities:

Would you like to get gas from coal without heating the coal? To make an inflammable gas that will dissolve in certain liquids as easily as sugar does in coffee? To produce a gas that burns with a flame you can hardly perceive? Or to create fiery bublles of gas, jumping about like grasshoppers, from simple everyday chemicals? These are some of the curious and interesting experiments with hydrocarbon gasses that any amateur chemist can easily perform.

The gentleman in the illustration is collecting methane, the gas that bubbles up through the water of marshes. He is collecting it by stirring up the muddy bottom and trapping the ascending bubbles under an inverted funnel.

For those without a nearby swamp, the article also explains how to mix up a batch in the lab.

The article also explains how to make acetylene. This involves first creating some chlorine gas, capturing it in a bottle, and then adding some calcium carbide and water. As the resulting acetyline reacts with the chlorine gas, it produces a flash of light and a tiny cloud of soot. “With the bombardment proceeding at the rate of several explosions a second, the bottle resembles a miniature battlefield.”

For the aspiring young mad scientist, this article should be great inspiration for a first-place science fair project.