Thermite Formula: Ingredients, Tips, and Everthing You Need to Know

A step-by-step guide to making thermite at home, complete with safety information

Co-authored by Bess Ruff, MA and Johnathan Fuentes

Last Updated: February 21, 2023 References Approved

Of all the do-it-yourself chemistry experiments found online, there’s almost nothing cooler—or maybe hotter—than a thermite reaction. With a fire that reaches 2,200 °C (3,990 °F), this simple mixture of rust and aluminum powder burns hot enough to turn rocks into lava. Thermite is famously used for welding since it produces molten iron as a byproduct, though it has tons of other applications too. Though you can make thermite yourself with the right preparation and safety gear, remember that it is extremely dangerous and should only be done in a lab.

Things You Should Know

Thermite is a 1:3 mixture (by mass) of metallic aluminum and iron oxide. It burns at 2,200°C (3,990 °F), producing molten iron, and is often used for welding.^{[1]
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Making thermite is extremely dangerous. Take safety precautions like wearing a welding mask, fireproof apron, and protective clothing.
To make thermite, combine powdered iron oxide and aluminum powder in a ceramic container. Insert a magnesium strip into the mixture, light it, and stand back.
Do not attempt to extinguish burning thermite with water. Let it burn out. Never remove your safety gear when working with thermite.^{[2]
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Part 1

Part 1 of 2:

Safety Precautions

1
Select an area that’s free of flammable material. Ideally, make thermite in a laboratory equipped with heat screens and ventilation. Making thermite outside is not recommended because wind can carry burning material away from the reaction. Whatever site you choose, make sure there is nothing that can burn within a 4 meter (13.1 ft) radius of the reaction. Make sure that there no metals with low melting points, such as lead, tin, cadmium, or zinc, within a 4 meter (13.1 ft) radius either.^{[3]
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- Do not make thermite inside your home or garage.
- Keep children and pets away from the thermite. Never let children do this experiment.
2
Use ceramic containers rather than metals to minimize fire risk. Since you'll be burning metals, the thermite fire can burn through a lot of substances, including thick metals. Ceramics, such as clay flower pots, can hold the fire without melting.^{[4]
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- Look online for ceramics labeled as having a high heat point. Remember, thermite burns at 2,200 °C (3,990 °F).
- Even ceramics can break from excess heat. Stand back once the reaction starts in case the container breaks, spreading burning material.
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3
Wear a welding mask to protect your face and eyes. In addition to being extremely hot, thermite emits UV radiation that can damage your vision. A welding mask provides the best protection because it's designed for use with burning metals, such as thermite.^{[5]
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- Do not look into the flame directly. Use a welder's mask or welder’s glasses. Looking at the flame directly could cause permanent eye damage.
- If you don't have a welding mask, wear a pair of dark sunglasses with full UV protection. However, the thermite can still damage your eyes if you look at it directly.
4
Put on safety gear, including gloves and a fireproof apron. Choose a pair of sturdy, heatproof gloves, and make sure the fireproof apron covers your whole body. Wear thick sleeves, pants that cover your exposed skin, and close-toed shoes.^{[6]
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- Thermite is very dangerous, so protective gear is essential.
- Take precautions to prevent your clothing from catching fire. Burning clothing is difficult to remove and can cause severe burns.

Part 2

Part 2 of 2:

Making the Thermite

1
Use powdered iron oxide, aluminum powder, and a strip of magnesium. Choose finely powdered iron oxide so that it reacts easily with the aluminum, forming thermite. Make sure the magnesium strip is very thin so that it burns easily and ignites the material. For a basic thermite experiment, you'll need 3 grams of aluminum powder and 9 grams of iron oxide.^{[7]
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- Do not try to grind up the metals into powder yourself, as this is dangerous. Buy them in jars from a chemical company or online. Aluminum powder can also be obtained from a paint store or even an Etch-a-Sketch.
2
Dry out your iron oxide in an oven or over a Bunsen burner. Set the oven on a medium temperature, such as around 200 °F (93 °C). Heat the iron oxide for 1 hour. If you're using a Bunsen burner, place the iron on an evaporating dish over the flame for 1 hour.^{[8]
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- Allow the iron oxide to completely cool before you do the experiment.
- Use caution when using a bunsen burner. The open flame is a fire risk. Never leave it unattended. When you’re finished, make sure the gas supply is shut off completely.
3
Mix the aluminum powder and iron oxide on a sheet of paper. Add 3 grams of aluminum powder and 9 grams of iron oxide. Swirl the metals together or shake them between 1 piece of paper and another. Continue to blend until they are fully mixed.
- If you increase the quantity of the metals, stick to a 1:3 ratio (by mass) of aluminum to iron oxide. But don’t work with larger amounts until you’re experienced in working with thermite, since this experiment is very dangerous.
- Never mix them in a metal container, as this can contaminate the project or cause an unwanted reaction.^{[9]
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4
Pour the mixture into a ceramic container, such as a clay flower pot. Ceramics are less likely to melt with the heat of the thermite. It's best to place the ceramic container into a second ceramic container, in case the first one shatters from the heat.^{[10]
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- Do not light thermite on an ice block, as it may cause a dangerous explosion. Ice is not an option for controlling the heat of the flame.
5
Insert the magnesium strip into the mixture. Make sure that your magnesium strip is at least 6.5 cm (2 inches) long.^{[11]
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- Use a longer magnesium strip to give yourself time to step back before the thermite ignites.
6
Light the magnesium strip with a propane torch or stick lighter. Stand at least 4 meters (13 feet) away from the thermite to watch the reaction.^{[12]
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- Use sparklers to light the thermite if you don’t have magnesium available.
- Keep your safety gear, especially your eye protection, on at all times.
- Do not use matches to light the magnesium strip (or sparkler) since matches could drop burning material into the thermite, causing it to ignite while you are standing next to it.
7
Let the thermite burn out completely. Remember: a thermite reaction is irreversible once it starts. Don’t try to extinguish it using water. This could cause an explosion.^{[13]
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- Keep a fire extinguisher nearby in case of secondary fires.^{[14]
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  Research source} You cannot use a fire extinguisher to put out the reaction itself, but you can use it to prevent fire from spreading to other areas once the reaction has stopped.

Community Q&A

Question

What can you use Thermite for?

ChemGenius

Community Answer

Making iron nodes. It used to be used to weld train tracks together. The military uses it to quickly destroy valuable information or equipment in a hurry during war.
Question

Is it possible to use aluminum oxide instead powdered aluminum?

Community Answer

No. Thermite is an oxidation of the aluminum powder to aluminum oxide and a concurrent reduction of the iron oxide powder to iron. The aluminum and iron oxidation and reduction, respectively, form the two half cells of the thermite redox reaction. If you start with aluminum oxide and iron, you have the stable products after a thermite reaction, not the unstable reagents needed to make a thermite reaction.
Question

Can the thermite reaction cause an explosion or just cause spontaneous combustion?

ChemGenius

Community Answer

For iron thermite, it burns violently. If you replace the iron oxide with copper oxide it explodes. A thermite mixture made from iron oxide & alumimium powder mixed together can explode for no reason.

Warnings

Making thermite is extremely dangerous. A thermite reaction can cause severe burns and nearby areas to catch fire.

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Keep children and pets away from your thermite.

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Keep a fire extinguisher nearby for secondary fires only. You cannot put out a thermite fire using a fire extinguisher.

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Use a propane torch or stick lighter to ignite the magnesium strip. Don’t use a match or anything that could break and fall into the thermite. This could cause it to ignite while you are standing next to it.

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Do not let children participate in this experiment in any way.

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Allow the thermite to burn out completely. A thermite reaction is irreversible once it starts.

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Do not add anything to the thermite once it ignites.

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Stand at least 4 meters (12 feet) back from the thermite after you ignite the magnesium strip.

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Put a ceramic dish under the thermite to catch the resulting molten iron.

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Don’t ignite thermite on public property, streets, sidewalks, or other thoroughfares.

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Check the laws of your country, region, and city to ensure that making thermite is not explicitly illegal, or that doing so does not violate other laws. For example, in the U.K., there are strict laws regulating the creation of incendiary devices.^{[15]
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Call emergency services immediately if the thermite causes a secondary fire, or if you or someone in the vicinity is injured.

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Don't put thermite on ice. This could cause an explosion.^{[16]
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