Thermite

Thermite is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brief bursts of heat and light in a very small area.

Description of what it is like

A heavy, stable powder (usually grey or reddish depending on the oxide used). It is stable at room temperature and very difficult to ignite without a high-temperature starter.

Origin and where to find it

• Not natural: Must be prepared from refined metals and oxides.
• Components: Aluminium powder and Iron Oxide (rust).

Minimum processing required

1. Powdering: Grinding aluminum into a fine powder (e.g., from scrap or foil).
2. Oxide Preparation: Gathering iron oxide (rust) and ensuring it is dry and powdered.
3. Mixing: Thoroughly mixing the two powders.
4. Ignition: Requires a high-temperature source like a magnesium ribbon or a specialized “igniter” mix (like potassium permanganate and glycerin).

Tools needed to work on it

• Ball Mill: For fine powdering of aluminum.
• Sieves: For consistent particle size.
• Refractory Crucible: To contain the reaction (which reaches ~2500°C).

Common forms of use

• Welding: Molten iron from the reaction flows into a mold to join rails.
• Demolition: Cutting through thick steel beams.

Possible substitutes

• Oxy-acetylene torch: For cutting and welding.
• Electric Arc: For high-temperature melting.

Limitations and common failures

• Ignition failure: If the powders are not fine enough or the ignition source is not hot enough, the reaction won’t start.
• Moisture: Damp powder may react poorly or splutter dangerously.

Risks and safety

• Extreme Heat: Reaches temperatures that melt almost any metal.
• UV Radiation: The reaction produces intense light that can damage eyes (use welding goggles).
• Difficult to Extinguish: Once started, it should never be sprayed with water (risk of steam explosion), and while dry sand can be used to contain or redirect the reaction, it will not fully extinguish the thermite itself.

Related materials

• Aluminium: The fuel.
• Iron Oxide: The oxidizer.
• Iron: The product.