Bulgarian umbrella Bulgarian umbrella A Bulgarian umbrella is an umbrella with a hidden pneumatic mechanism which injects a small poisonous pellet containing ricin. It has a hollowed stalk into which the pellet neatly sits. Such an umbrella was allegedly used in and named for the assassination of the Bulgarian dissident writer Georgi Markov on 7 September 1978 (the birthday of the Bulgarian State Council chairman Todor Zhivkov, who had often been the target of Georgi Markov's criticism) on Waterloo Bridge in London. Markov died three days later. It was also allegedly used in the failed assassination attempt against the Bulgarian dissident journalist
Umbrella gas used by riot police. In the 1950s Frei Otto transformed the universally used individual umbrella into an item of lightweight architecture. He developed a new umbrella form, based on the minimum surface principle. The tension loaded membrane of the funnel-shaped umbrella is now stretched under the compression-loaded bars. This construction type made it technically and structurally possible to build very large convertible umbrellas. The first umbrellas of this kind (Federal Garden Exhibition, Kassel, 1955) were fixed, Frei Otto constructed the first convertible large umbrellas for the Federal Garden Exhibition in Cologne 1971. In 1978 he built a group of