People said this experiment was impossible, so I tried it - Thermite Part 1

A chemical reaction discovered over 125 years ago that releases tremendous amounts of heat, can liquefy metal, and exceeds temperatures of 2,000 degrees Celsius.

• Not an explosive, but can cause explosions • Reactants are so inert they can withstand a blowtorch indefinitely • Used by Hollywood for nuclear bomb effects

In its most common use over the past century, it has helped move billions of people all over the world.

Has become one of the most important applications in modern industry.

In the late 1800s, brothers Karl and Hans Goldschmidt worked in their father's chemical factory making dyes for fabrics, studying chemistry under Robert Bunsen.

• Good dyes were hard to come by and faded quickly after use • Some required large quantities of exotic insects • Bright, colorfast dyes commanded high prices • Pure metals were essential for making quality dyes

Hans developed a novel idea to react metal oxides like chromium oxide with aluminum metal, hoping the oxygen would swap partners to form pure metal and aluminum oxide.

This type of reaction became known as an aluminothermic or thermite reaction.

Derek visits Electro-Thermit in Germany, a direct descendant of Goldschmidt's company, to replicate Hans' first successful reaction using copper as a comparable alternative to chromium.

• 300 grams of thermite powder poured into a crucible • Mixture ignited, releasing impressive energy • Creates bright, glowing hot reaction

Thermite reactions typically exceed 2,000 degrees Celsius, reaching up to 2,500 degrees because aluminum forms very strong bonds with oxygen, releasing far more energy than required to break the initial copper oxide bonds.

The reaction is so bright it feels like staring at the sun, making it difficult to judge intensity and almost always exceeding expectations.

Derek and the team attempt an experiment no one has seen before by cutting a crucible in half and attaching two pieces of four-millimeter thick thermally resistant glass as windows into the reaction.

• People said it would be impossible • Claimed viewers wouldn't see anything or glass would shatter • Glass has melting point around 1,700 degrees Celsius, lower than the reaction temperature

The glass will melt slowly enough to contain the reaction, leaving only a thin layer at the end, allowing observation of the process.

For this reaction, iron thermite is used—a combination of iron oxide and aluminum metal.

The reaction reveals a pulsing pattern that even the professionals at Electro-Thermit had never observed in 100 years of work.

• Reaction starts at igniter and expands outward in all directions • Appears organic, like spreading ants or mold • Proceeds in distinct bursts with pauses between advances

• Mixture of grain sizes may require specific ratios for efficient reaction • Pockets may react to less-ideal ratios until heat triggers the next pocket • Air between grains heats up, expands, and pushes unreactive material away

Derek uses a probe lens to film from below as thermite sits on glass, capturing the closest footage of a thermite reaction ever filmed, showing the bursting and pausing process clearly.

Once all thermite has reacted, molten metal is ejected from the crucible top and the liquid sloshes violently inside.

• Molten mixture reaches temperatures that cause some materials to boil • Aluminum boils around 2,500 Celsius • Iron boils above 2,800 Celsius • Manganese boils at just 2,000 Celsius

Liquid iron is more than twice as dense as liquid aluminum oxide, so iron settles to the bottom while aluminum oxide floats to the top, enabling natural separation.

• Iron flows out first when metal melts through crucible bottom • Iron has viscosity like water, visible and splashing • Slag follows afterward, flowing like warm honey

A cobblestone made of limestone is placed inside the crucible, and thermite is poured on top and ignited.

The cobblestone breaks into pieces as it rises to the surface, just like slag, demonstrating density-based separation in action.

Less dense ordinary rocks like cobblestones rise to the surface alongside slag, while denser metal drops to the bottom.

This density-based separation is key to producing high purity metal in the crucible.

Hans Goldschmidt patented the process in 1895 and described it as extraordinarily simple yet remarkable for its surprising effects.

One of the first applications was welding metal parts in remote locations where bringing tons of welding equipment was impractical.

• Shipping companies were among the first customers • Could fix broken shafts in the middle of the ocean • Required only two people and a bucket • Allowed ships to reach home instead of being lost

Could fix cracks in engine blocks and was extremely mobile compared to traditional welding equipment.

• Iron thermite produces steel, not pure iron • Carbon and other alloying elements included in the thermite powder • Pure iron is soft and corrodes immediately, so steel is the practical product

The majority of thermite produced today is steel thermite rather than other metal thermites.

After the Cold War, thermite was used to destroy gun barrels from tanks by inserting it into the barrel and igniting it to weld and destroy the barrel permanently.

• Very quick process • Very safe compared to explosives • Very final—weapons become completely unusable afterward

Modern thermite use includes destroying information by using heat to exceed the Curie temperature, where magnets lose their magnetism.

Information stored on magnetic hard drives becomes unrecoverable at high enough temperatures.

• Thermite tile formulation differs from powder version • Looks like a normal piece of tile • Can be handled safely before ignition

When ignited on a laptop in four corners, the thermite tile generates heat for about 10 minutes, creating molten metal that completely destroys the device and any data on it.

Despite releasing tremendous energy, thermite is not well-suited for explosive purposes because both reactants and products are solids and liquids, not gases.

• Explosions with gas products expand unpredictably • Thermite energy can be calculated precisely • Control allows calculating exact megajoules over time

The controllability enables using thermite to demolish structures where explosives would cause too much collateral damage.

In 1957, thermite charges were used to carefully melt and remove the burnt steel dome from the Reichstag building in Berlin without damaging the surrounding historic structure.

• Mixture includes pieces of pure steel that don't participate in reaction • Steel pieces absorb heat as they melt • Help control reaction rate and temperature reached

• Key parameter is when metal starts flowing out the crucible bottom • Too-short tap time means metal and slag don't fully separate • Too-long tap time causes metal to dissolve more crucible material and cool down

Different damping percentages (12% vs 25%) can be used to control whether metal comes out hotter or colder.

The chemistry of the steel actually changes the longer it stays in the crucible, making precise tap time control essential for quality.

• Mill scale is the basic starting material • Mixture of different iron oxides from steel rolling • Forms when hot steel surface oxidizes during hot rolling

• Trucks deliver mill scale about once or twice daily • Material is dried because thermite and water don't mix • Iron oxide is elevated on spiral ramp to top floor for processing

• Particles separated into different sizes and compositions • Mixed with aluminum powder • Every portion has very defined reactivity • Ensures desired reaction and steel chemical qualities

Portions are bagged up individually and stored in warehouses, with multiple large warehouses required to hold all thermite inventory.

Despite tremendous energy in thermite and large quantities stored, the facility is safe because thermite requires specific conditions to ignite.

• Derek attempts to ignite thermite with a lighter—fails • Tries with a propane torch—still fails • Even when glowing orange hot, thermite won't ignite under normal conditions

Thermite can actually melt from extreme heat without igniting, proving it's extremely difficult to light.

• Aluminum particles are covered in aluminum oxide layer • Only violent heating breaking down this layer in many particles starts reaction • Aluminum oxide acts as a secret stopper

Thermite has very high activation energy, making it impossible to start with a lighter or propane torch.

• Barium hydroxide igniters are used—same material as in sparklers • Gets hot enough to break through aluminum oxide layer • Starts the reaction deliberately

Ignition temperature is set so high it can only be lit intentionally, preventing accidental ignition.

Once the reaction starts, there is no way of stopping it.

Derek filmed in Germany for five full days, with this being only a taste of what's coming in future videos.

• How thermite reacts with its environment • The most common application: welding railroad tracks together

Millions of video viewers have probably ridden on trains and are very likely to have ridden over thermite welds.

The expert at Electro-Thermit confirms that essentially 100% of train viewers will have experienced thermite-welded railroad tracks.