During World War II, coffee was a strategic resource—no less critical than gasoline or ammunition. The US Army shipped over 2 million kilograms of coffee to its soldiers every month—delivered as instant powder (Type II Instant Coffee) and roasted beans in tin cans (C-Ration coffee). Alertness and morale depended on this drink. But a problem emerged that no one had anticipated: coffee bombs.
Freshly roasted coffee releases carbon dioxide (CO₂). In the first days after roasting, the emission peaks—up to 500 ml of CO₂ per kilogram. In airtight packaging, the gas builds pressure. In tropical conditions (Pacific Theater, New Guinea, Solomon Islands), at temperatures of 35–40°C, the pressure could reach 2–3 atm. Coffee cans bulged, swelled, and in rare cases—burst with a sound like a gunshot. Warehouse workers called them "coffee mines."
In 1943, Army Ordnance engineers conducted a study: Type II coffee (instant, in tin cans) released gas more aggressively than acetone-based munitions. Hazardous materials classification: coffee—Class 9 (miscellaneous dangerous goods), ammunition—Class 1. A damaged can could detonate, scattering shrapnel and hot coffee granules. No one could predict which can in a container would explode first.
The problem lay in degassing—the natural process of CO₂ release after roasting. Traditional packaging (sealed ends, airtight cans) didn’t allow the gas to escape. Minor leaks—through micro-pores in welded seams—helped, but not enough; pressure kept building.
In 1944, a team of engineers from MIT led by Dr. William Richard proposed using a one-way degassing valve—a thin rubber/foil membrane that opens at internal pressures above 0.1 atm and seals shut at normal pressure. The valve let CO₂ out but kept oxygen from getting in—a key factor in preserving freshness.
Prototypes were handmade from latex and foil. After successful tests at the Aberdeen Proving Ground (Maryland), where tropical conditions were simulated, the Army Standardization Board issued specification MIL-V-27561—the first military standard for the valve. By 1945, the valve was built into every tin can of Type II instant coffee, as well as into bags of green beans for maritime transport.
After the war, the technology transitioned into the commercial sector. In the 1960s, the Italian company Goglio developed an automatic machine for installing valves on flexible foil pouches. By the 1970s, the valve became standard for specialty coffee. Today, every coffee bag in the world (if it’s high-quality) has this valve—a direct line from WWII’s "coffee bombs."
👉 Safety vs. Freshness. The valve saved warehouses from explosions but also preserved aroma. Without it, fresh coffee couldn’t be stored for more than a week in airtight packaging.
👉 War—The Engine of Progress. A danger born from logistics spawned an invention now considered "obvious" for any coffee drinker.
👉 The term "Type II" survived only in military documents. In civilian life, it vanished—but the valve remained.
The coffee that nearly blew up WWII logistics gave us one of the most important details in modern packaging. Sometimes, the most ordinary things (a tiny valve on a bag) have a dramatic origin. And it’s always worth remembering: what’s today’s marketing gimmick was yesterday’s matter of life and death.