Propaganda balloons get their second wind

In 2021, a large metal trunk was discovered in the attic of the Danish War Museum in Copenhagen, containing two complete World War Two propaganda balloons, constructed by the British Royal Air Force to drop leaflets over Germany. Because the balloons were designed to self-destruct and often ended up in random locations, very few still exist today. Drones and planes have since replaced balloons, and this discovery provided a unique opportunity to study older communication technology. Optical microscopy revealed that the 350 cm tall and 300 cm wide balloons were sewn from fine cotton coated with vulcanised rubber, similar to that used in raincoats and military uniforms. One balloon was coated in talcum powder, which protects against water, acids, and oxygen. Numerous red spots, cracks, and damage to the textile were due to reactions between moisture, oxygen, and sulfur in the rubber.

A preservation strategy has increased knowledge of the propaganda balloons’ significance and availability after 80 years of anonymity in a metal trunk. The balloons were cleaned, leaving only a thin layer of protective talcum, packed flat in transparent, flexible pouches, and sealed to slow down their degradation and preserve them for future generations.