How to Make Thermite

What is Thermite?

Thermite is a pyrotechnic composition usually consisting of metal powder and a metal oxide. It is not usually explosive, but it does create extremely high temperatures in a very small area for a short period of time. For instance, aluminum/iron-oxide thermite temperatures are as high as 4500 degrees F.

Thermite is used for welding, metal cutting or boring, field-expedient metal repairs, science demonstrations, high temperature ignition, disabling military equipment (including artillery, document files, and hard drives), and other applications.

Making Thermite Using Red Iron Oxide

Having the correct balance of fuel and oxidizer is key to having a stable burn in a thermite reaction. The thermite recipe for red iron oxide and aluminum is 3 parts iron oxide red to 1 part aluminum fuel. In pyrotechnic compositions the finer the ingredients and more well mixed they are, generally the easier it is to ignite, and the faster the reaction will progress.

So our goals in selecting thermite ingredients are ease of ignition and a stable, non-explosive burn.

For this example, we are using Skylighter's -325 mesh red iron oxide and Skylighter's -325 mesh bright aluminum, which has an average particle size of 45 microns.

Thermite#1 Mixture

Ingredient Parts by Wt.    Parts by %
Red iron oxide -325 mesh 3 75   
Aluminum flake -325 mesh   1 25   
      Total   100%

To make a 4 ounce batch of thermite, first weigh out 3 ounces of red iron oxide. Then weigh out 1 ounce of aluminum powder. Dump them into a plastic tub, and put the top on. Shake them until the color is consistent throughout.

Then pass the mix through a 20-mesh or finer screen. If there are any clumps break them up with your fingers. Screen the mix two more times, or more, until you have a uniformly colored powder.

Note: Using a 40-mesh or finer screen will make the mix much easier to ignite.

This can be a dusty process, so be sure and do it an area where the aluminum dust will not cause a problem. Do not try this where air is moving. The better you mix the ingredient, the faster and hotter the reaction will be. Thermite needs a very high temperature to ignite it.

Your thermite kit comes with 6 gold sparklers. The iron in them burns at around 1800 degrees F.

Here's how to use sparklers to ignite your thermite. Place your thermite mix in a plastic tub. Make a hole near the bottom on the side of the tub big enough for a sparkler to go through.

Push 1 to 2 of inches of the sparkler through the hole in the side of the tub into the mix inside. Leave at least 2-3 inches of your sparkler sticking out. Place the plastic tub on a metal surface that want to burn through. Light the sparkler, and get back 40 or 50 feet.

WARNING: Do NOT attempt to ignite your thermite by dipping your sparkler into the mix by hand. The mix can and does ignite violently, and will spray you with burning metal.

WARNING: A violent ignition of thermite can throw molten metal in all directions. Do not stand close to the mix when it is igniting or burning.

TIP: If you have trouble igniting your thermite with a sparkler, try mixing some magnesium powder or chips into a small amount of thermite mix. Then you should be able to ignite the magnesium mix using your sparkler.

WARNING: Thermite burns extremely hot and produces molten iron slag that can melt though a car's engine block! Burning thermite can spatter molten iron a long way from the burning pile. Stay as far back as you can. And make sure there is nothing nearby that can catch fire. Start your thermite experiments with small amounts at first, until you understand how it behaves, and how far it will throw molten metal slag.

WARNING: You cannot extinguish a thermite fire with water. Do not attempt to put the fire out with water, or you may have a violent, steam explosion, which can throw molten slag as well. Likewise, do not use any wet materials to attempt to extinguish the fire.

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