Science fairs used to be a thrilling mix of curiosity, creativity, and—let’s be honest—some very questionable safety practices. Back in the day, kids experimented with electricity, fire, and even radiation, often with little more than a vague warning from a teacher. Parents cheered on projects that would never be allowed today, and many budding scientists had close calls with explosions, toxic fumes, and flying debris. While these experiments were impressive at the time, looking back, it’s a wonder more kids didn’t end up with singed eyebrows or worse.
1. Homemade Volcanoes with Real Explosions
The classic baking soda and vinegar volcano was a harmless crowd-pleaser, but some kids took it much further. Instead of simple foamy eruptions, students experimented with real explosives like potassium permanganate and glycerin or even gunpowder to create massive blasts. The bigger the eruption, the better the grade—or at least that’s how some young chemists saw it. National History Museum is all too glad to provide instructions for the latest generation of curious minds.
Of course, this led to more than a few unintended fires, singed hair, and even small-scale detonations in school gymnasiums. Teachers often had to intervene when students got a little too ambitious with their volcanic experiments. Eventually, safer alternatives became the norm, but early science fairs had more than a few literal fireworks.
2. Cloud Chambers for Detecting Radiation
In the mid-20th century, ambitious students wowed judges with cloud chambers—devices that made invisible radioactive particles visible. Using dry ice and sometimes actual radioactive materials, these projects demonstrated cosmic rays and radiation trails in a misty, eerie glow. It was a great way to learn about physics, but the problem was… well, radiation. Institute of Physics breaks down just what is scientifically happening with this experiment.
Many students used radium-dial watch hands, uranium ore, or even smoke detector components, all of which contain radioactive elements. While the levels were usually low, handling radioactive materials without proper shielding or knowledge was definitely a bad idea. These projects quietly disappeared from fairs as awareness of radiation risks grew.
3. Tesla Coils and High-Voltage Fun
Tesla coils are undeniably cool, throwing off sparks and creating electric arcs that seem like magic. Many students built small versions to demonstrate wireless electricity, sometimes lighting fluorescent bulbs just by holding them near the coil. The problem? Tesla coils operate at tens or even hundreds of thousands of volts, and homemade versions were often built without proper insulation. This device is still popular, and Instructables dives deep into how to construct one from start to finish.
A miscalculated design could send an electric shock across the room, and some kids tried to create “lightning gloves” by conducting electricity through their bodies. While these projects were thrilling to watch, one slip-up could mean a nasty jolt or worse. Today, high-voltage experiments are strictly monitored, but back then, they were just another cool science fair attraction.
4. Homemade Rocket Fuel Experiments
Some kids weren’t satisfied with baking soda-powered model rockets—they wanted real thrust. Using chemicals like potassium nitrate and sugar, or even more volatile mixtures, students created solid rocket fuel for their DIY propulsion systems. These projects were meant to demonstrate Newton’s laws of motion, but more often, they demonstrated the laws of unintended explosions. The National Air and Space Museum offers ways to cross some classic experiments with one another.
Many of these rockets didn’t exactly launch straight up. Some exploded on the pad, others veered off in unpredictable directions, and a few even started fires. Eventually, schools cracked down on homemade rocket fuel, though plenty of kids still experimented in their backyards.
5. Ether-Based “Instant Ice Cream”
Science fairs in the past often included chemistry-based food experiments, and one particularly risky project involved using ether or liquid nitrogen to make instant ice cream. Ether was once a common refrigerant and anesthetic, and kids used it to rapidly freeze ice cream mixtures, creating a deliciously cold treat.
The problem? Ether is extremely flammable and highly toxic when inhaled. A single spark could ignite it, and repeated exposure could cause serious health issues. Eventually, science fairs banned ether experiments, though liquid nitrogen, when used properly, remains a safer (and much more legal) alternative.
6. Homemade X-Ray Machines
Believe it or not, some enterprising students actually built functioning X-ray machines for their projects. Using vacuum tubes, high-voltage transformers, and sometimes scavenged parts from old televisions, they created devices that could see through objects. In theory, this was an incredible demonstration of physics.
In practice, these homemade machines often emitted unshielded radiation, posing serious risks to both the student and anyone standing nearby. Since the dangers of X-ray exposure weren’t widely understood at the time, these projects were surprisingly common in the mid-20th century. Today, no school would allow a student to bring in a homemade radiation device—but for a while, it was just another science fair wonder.
7. Exploding Hydrogen Balloons
Hydrogen is lighter than air and perfect for balloon experiments, but some students couldn’t resist the urge to add a little fire. Many kids demonstrated the flammability of hydrogen by igniting balloons filled with the gas, resulting in loud explosions and dramatic fireballs. The bigger the balloon, the more exciting the boom.
Unfortunately, this experiment was more dangerous than it looked. Hydrogen burns extremely hot, and even a small mistake could lead to burns, injuries, or even structural damage if done indoors. Science fairs eventually replaced this demonstration with safer alternatives, but those who witnessed a hydrogen balloon explosion in person will never forget it.
8. Mercury Experiments with Bare Hands
For years, mercury was a fascinating element for students to play with—it was liquid metal, after all! Science fair projects often included demonstrations of how mercury conducted electricity, formed strange beads, or even coated pennies in a shiny silver layer. Many students (and teachers) handled it directly, letting it roll around in their palms.
Of course, we now know that mercury exposure can cause serious neurological damage. Breathing in mercury vapors or absorbing it through the skin is extremely hazardous, yet for decades, it was just another fun science fair activity. Once schools realized the long-term dangers, mercury was banned from classrooms, but many students from past generations still remember playing with it.
9. Static Electricity Generators Gone Wrong
Van de Graaff generators are a staple of science education, making hair stand on end and generating shocking demonstrations—literally. But some students took static electricity experiments too far, creating charge-building devices powerful enough to knock people over. With no grounding precautions, these machines sometimes delivered more than just a small zap.
In some cases, students tried to use static electricity to power light bulbs, leading to unexpected (and painful) shocks. Others experimented with flammable materials, creating accidental sparks near combustible substances. While static electricity remains a fun physics lesson, the wild, unregulated experiments of the past often left students (and teachers) jolted.
10. Acid and Metal Reactions in the Classroom
Some students wanted to demonstrate real chemistry reactions, leading to one of the most dangerous classic experiments—mixing acids with metals. Whether it was hydrochloric acid with zinc to produce hydrogen gas or sulfuric acid to dissolve materials, these projects were explosive, corrosive, and often performed with minimal safety gear.
Accidents were common, from acid spills to unexpected gas releases that left students coughing. Safety glasses weren’t always required, and protective gloves were rare, meaning burns and chemical stains were almost a rite of passage. Modern chemistry projects are much safer, but back in the day, kids were practically doing mad scientist experiments right in the school gym.
These science fair projects were creative, educational, and often wildly unsafe. While they pushed the boundaries of discovery, they also tested the limits of what students (and teachers) could get away with. Looking back, it’s amazing that so many kids made it through their science fair days unscathed, proving that sometimes, the best experiment is simply learning from past mistakes.
