Copper wool is a material made from fine copper wire filaments, often used in cleaning applications or for pest exclusion. Copper wool is not flammable in the conventional sense of the word. Unlike materials that catch fire and sustain a flame, copper is highly resistant to ignition under normal atmospheric conditions. Its fundamental chemical and physical properties prevent the rapid, self-sustaining combustion reaction with oxygen that defines a flame.
Why Copper Does Not Burn
The inability of copper to burn comes down to its stable elemental structure as a metal. Combustion is a rapid chemical reaction between a substance and an oxidant, usually oxygen, that produces heat and light. Copper is a relatively unreactive metal, indicating its low tendency to participate in a rapid oxidation reaction.
The metal’s electronic configuration contributes to its stability, making it chemically unsuited for the quick, exothermic reaction necessary to start and sustain a fire. At standard temperatures, copper reacts with oxygen and carbon dioxide over long periods to form a protective layer, known as a patina. This slow process is a form of oxidation but is not a fire hazard. The massive energy input required to force copper into a rapid reaction is not met by common ignition sources like a match or a spark.
What Happens When Copper Wool Gets Very Hot
When copper wool is exposed to extreme heat, it undergoes physical and chemical changes related to its high melting point rather than bursting into flames. Pure copper melts at approximately 1,984°F (1,085°C), a temperature far higher than the heat generated by most accidental fires or common heat sources. The wool must reach this intense temperature before it begins to liquefy.
Before melting, a high heat source accelerates the reaction between copper and oxygen, resulting in a dark discoloration. This accelerated oxidation forms a layer of black copper oxide on the surface. This tarnishing is a slow chemical change that consumes heat rather than releasing it quickly, preventing a self-sustaining combustion reaction. The wool will simply glow red hot and eventually melt into beads if the heat is maintained.
Copper Wool vs. Steel Wool
The distinction between copper wool and steel wool is significant and addresses the likely reason for confusion about flammability. Steel wool is made primarily of iron, which is chemically much more reactive with oxygen than copper. The fine, shredded nature of steel wool creates a massive surface area, allowing a large number of iron atoms to be simultaneously exposed to oxygen.
When a small amount of energy, such as a spark from a battery, is applied to steel wool, the iron reacts rapidly with oxygen to form iron oxide, or rust. This highly exothermic reaction releases sufficient heat to ignite adjacent strands, causing the wool to glow brightly and visibly burn without a flame. The energetic oxidation and high surface area sustain a chain reaction in steel wool.
Copper wool, conversely, does not have this energetic chemical pathway available. Even with the high surface area created by the thin strands, copper atoms will not readily combine with oxygen in a rapid, heat-releasing reaction. This difference means that while steel wool is an effective fire-starter, copper wool is a non-combustible material that poses no similar ignition risk.