Gunpowder, the general term for chemical propellants, is not a uniform substance, and its reaction to water depends entirely on its composition. The two main types, traditional black powder and modern smokeless powder, behave fundamentally differently when exposed to moisture. Water does not typically cause either type of propellant to explode; instead, it affects the powder’s ability to ignite and burn predictably. The primary concern is whether water renders the substance temporarily inert or causes permanent chemical damage.
The Immediate Impact on Black Powder
Traditional black powder is a mechanical mixture of potassium nitrate (saltpeter), charcoal, and sulfur. This composition makes it highly vulnerable to water because potassium nitrate, which serves as the oxidizer, is water-soluble. The oxidizer provides the oxygen necessary for combustion, allowing the powder to burn without drawing oxygen from the air.
When black powder absorbs water, the moisture dissolves the potassium nitrate, separating it from the charcoal and sulfur particles. As the water evaporates, the dissolved saltpeter recrystallizes, creating a hard, solid mass that binds the components together, a process known as caking. This clumping changes the physical structure required for a fast, consistent burn rate.
The resulting caked mass is essentially useless as a propellant because the intimate mixing required for proper deflagration is lost. The powder will either fail to ignite or burn extremely slowly and unpredictably. While water does not cause an explosion, it effectively destroys the powder’s ability to function as a propellant.
Smokeless Powder’s Reaction to Water
Modern smokeless powder, the standard propellant today, is fundamentally different, based on nitrocellulose, often mixed with nitroglycerin in double-base formulations. It is manufactured to be significantly more water-resistant than black powder and does not immediately dissolve or cake. Water exposure primarily impacts performance and long-term stability rather than causing immediate physical destruction.
Initial exposure to water dampens the powder grains, which dramatically lowers the propellant’s burn rate. This reduced performance leads to unreliable and inconsistent muzzle velocities, making the ammunition unusable. Drying the powder may restore some functionality, but water’s more serious effect is accelerating chemical degradation over time.
Smokeless powder naturally breaks down over time, producing acidic byproducts. Manufacturers include chemical stabilizers, such as diphenylamine, to neutralize these acids and maintain the powder’s integrity. Water accelerates this degradation process, consuming the stabilizers faster. Once the stabilizers are depleted, the powder can become chemically unstable, potentially leading to spontaneous ignition or dangerous, unpredictable burn rates.
Salvaging Wet Propellants and Safe Disposal
Attempting to dry and reuse any wet propellant, especially smokeless powder, is strongly discouraged due to the potential for unpredictable and dangerous performance. Even if the powder appears dry, the loss of chemical stabilizers due to water exposure is irreversible. Reusing chemically degraded powder can result in catastrophic firearm failure caused by pressure spikes and dangerously inconsistent burn rates.
The safest approach for wet or deteriorated smokeless powder is proper disposal, often involving consulting local authorities or the powder’s manufacturer. Manufacturers recommend disposing of small amounts by spreading the powder thinly on a non-flammable surface in an isolated outdoor area and igniting it, using a long ignition train to retreat to a safe distance. Alternatively, because smokeless powder is biodegradable, it can be spread thinly on a lawn or garden, where it will break down safely into the soil.
Wet black powder is physically inert but should still be handled cautiously. It can be disposed of by dissolving it in a large quantity of water and flushing the resulting solution, though this method is not recommended for smokeless powder. The general safety rule is to never reuse powder compromised by moisture, heat, or age, prioritizing safety over salvaging the material.