Napalm is a highly effective incendiary weapon, essentially a gelled petroleum fuel. The direct answer to whether it burns on water is yes. Developed by chemists at Harvard University during World War II, the mixture was designed to burn longer and stick to surfaces, overcoming the limitations of liquid gasoline. This chemical innovation resulted in a substance that not only ignites easily but also resists water as a primary means of extinguishment.
What Makes Napalm Stick and Burn
Napalm is a volatile petrochemical, typically gasoline or jet fuel, thickened by a gelling agent. The original formulation, Napalm-A, used aluminum salts of naphthenic and palmitic acids to create the jelly-like substance, rapidly increasing the liquid’s viscosity.
The thickener prevents the fuel from flowing away quickly, sustaining a high-intensity, localized burn. Modern variants, such as Napalm-B, use gelling agents like polystyrene dissolved in benzene and gasoline. This newer composition creates a highly viscous gel that adheres tenaciously to whatever it touches.
The resulting mixture burns intensely, reaching temperatures between 800 and 1,200 degrees Celsius (1,470 to 2,190 degrees Fahrenheit). The gelled state allows the fuel to burn for minutes rather than seconds. This sustained heat output and adhesive quality are why the material is so effective.
The Physics of Burning on Water
Napalm’s ability to burn on water is a direct consequence of its chemical composition. The primary fuel component is a hydrophobic petroleum derivative, meaning it repels water and does not mix with it.
Napalm is also less dense than water, causing it to float on the surface. When deployed, the burning gel forms a floating layer separate from the water beneath it. The fire triangle (fuel, heat, and oxygen) is maintained because the floating napalm has unrestricted access to atmospheric oxygen.
Water usually extinguishes fire by cooling the fuel or smothering it by displacing oxygen. Since the floating napalm is separated from the bulk of the water, the water cannot effectively absorb the heat or displace the oxygen. Applying water can sometimes worsen the situation by splashing the burning gel and spreading the fire across a wider area.
Methods for Neutralizing Napalm
Since water is ineffective, neutralization requires interrupting the combustion process by targeting heat or oxygen. The most common method is smothering the flames to deprive the fire of oxygen. This is achieved by rapidly covering the burning material with non-flammable agents like sand, dirt, or specialized fire-retardant blankets or foams.
Specific dry chemical extinguishing agents are also used to break the chemical chain reaction of the fire. Specialized fire-fighting foams are engineered to create a physical barrier between the fuel and the oxygen supply. Due to the gel’s extreme viscosity and adhesive properties, any method must ensure complete coverage of the burning material.
Once the flames are extinguished, the sticky, hot residue remains and must be physically removed. Mechanical removal, such as scraping or wiping the residue off, is necessary to prevent re-ignition and stop the continued transfer of heat.
Evolution of Sticky Incendiary Weapons
The first-generation napalm (using aluminum soaps) was superseded by advanced formulations to improve stability and adhesion. The most significant evolution was Napalm-B, which utilized polystyrene as the gelling agent, often combined with benzene and gasoline. This new composition resulted in a gel that was less prone to degradation.
Modern incendiary devices, like the filler used in the MK-77 munition, incorporate additional ingredients for enhanced performance. These newer pyrotechnic gels may include powdered magnesium and sodium nitrate alongside petroleum oil and gasoline. Sodium nitrate introduces an internal source of oxygen, allowing the material to burn more intensely, even when atmospheric oxygen is limited.
Chemical refinement has maintained the fundamental principle of a sticky, sustained-burn fuel while increasing the material’s thermal output and reliability. The goal remains creating hydrophobic, viscous fuels that maximize the duration and intensity of the fire.