The December 1969 issue of Popular Electronics carried the plans for a 0.5 milliwatt laser. The magazine noted that there was a lot of interest in making such a device, and there were finally parts on the market to make one that met two important criteria: It had to be inexpensive enough for experimenter hobbyists, and it had to be safe. They deemed the 0.5 milliwatt device to be safe, given some precautions, and the whole project could be built for under $50.

The illustration above appeared in the February 1970 issue, and it depicted how the magazine viewed a few of its readers. In summary, they wanted to burn holes in things, and they wrote in to the magazine asking for plans to do that. In response, the editors made clear that they had no plans to do such a thing. To cause destruction to something, the laser would require a few watts. But eye damage could easily take place at just a few milliwatts. The 0.5 milliwatt laser was safe, but more powerful units were not, so the magazine didn’t want to be involved. “Out of responsibility and concern for our readers, POPULAR ELECTRONICS cannot suggest or recommend a laser of any higher strength than the one described in the article.”

For the young mad scientists, it’s probably possible to find dangerous lasers on eBay, but we don’t plan to help, either.  On the other hand, you can get safe low-powered laser pointers on Amazon.

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When I was a kid, my family received a mail order catalog from an outfit called Sunset House. You can see an example at this eBay listing.  The catalog was full of useful products you couldn’t find anywhere else, and one of them was a little blowtorch. The blowtorch had many uses, but the most practical, it seemed to me, was shown in the accompanying illustration, and that was for melting snow off the sidewalk. It seemed a lot simpler than shoveling, and I begged my parents to buy a blowtorch. They didn’t, and they pointed out one objection that I couldn’t counter–the water would just flow elsewhere and freeze. But still, it seems like a good idea, if you could just work this bug out.

And the idea has been around for at least a century, as shown by the cover of the January 1925 issue of Science and Invention. This one didn’t involve a flame, and the magazine didn’t think that my parents’ objection would be an issue, since it matter of factly stated that the snow would melt, “which runs off in the form of water.”

The magazine didn’t use a blowtorch. Instead, it used a method that might be of interest to young scientists in search of a science fair project. You simply sprinkle calcium carbide on the snow. It sinks in (you start the process by poking a few pieces into the snow) where it mixes with water, creating acetylene gas, which is highly flammable. You strike a match and set the snow on fire. You go forward sprinkling more calcium carbide ahead of the flames, and as the flames catch up, it sets fire to the snow you have sprinkled.

For the science fair, Junior simply finds a patch of snow outside the school, seeds it with calcium carbide, and sets it ablaze. It’s sure to take home the blue ribbon.

Junior does need to be reminded to be careful. The magazine article contained these warnings:

Great care must be exercised in sprinkling calcium carbide upon snow, so that when the gas is evolved and ignited, it will not set fire to shrubbery, trees or the house itself. Under no conditions should such a snow remover be used when a gale is blowing, and the individual drawing the mechanism over the road should always see to it that he heads into any slight breeze which may be blowing, so that his own clothes will not be ignited.

If Junior sets the school, or himself, on fire, then he’s unlikely to get the blue ribbon.

As with everything, Junior can get the calcium carbide on Amazon. If he wants to augment his project, he can explain how this chemical was used in miners’ lamps.

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Seventy years ago this month, the December 1954 issue of the British Radio Constructor noted that with “the festive season is drawing near, the reader may be interested in a simple little gadget which is guaranteed to liven up the party in more ways than one.” We’re sure that many of our readers might be similarly inclined.

This device is self-explanatory. It’s similar to a homemade Ford spark coil. An autotransformer steps up the voltage of a battery, and the coil also serves to operate a crude relay to convert the voltage to DC. The two handles are formed from the foil from a candy bar glued over wood. When it’s switched on, it make an inviting buzzing sound, and you ask your friends to grab the handles.

This might make an interesting science fair project, although we suggest that you determine first whether the science teacher has a sense of humor. If not, another project might be better suited.

Also, even though the resulting current is very low, since some of that current will pass directly through the heart of your subject, we wonder if it might be dangerous in some cases. Therefore, if you’re going to make this project, we wonder if it might be better to make sure that both electrodes go to the same side of the body.

We should note that as a youngster, we independently invented a similar device, making use of an old filament transformer and a buzzer. No harm was caused to anyone.

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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