A flour bomb consists of flour in a fragile container (e.g. a paper bag), thrown at a person or object to produce an inconvenient messy stain. Flour in a fragile container thrown at an object or person of derision is a classic protest method, along with the throwing of eggs and overripe tomatoes.
Uses
An example from May 2004 was the use of purple-dyed flour in condoms thrown at the Prime Minister of the United Kingdom, Tony Blair, in the chamber of the House of Commons of the United Kingdom by Fathers 4 Justice. The event highlighted the poor security methods employed in and around the Houses of Parliament at the time.
Flour bombs saw notable use during the controversial 1981 Springbok Tour at Eden Park in Auckland, New Zealand. In an attempt to disrupt the match, flour bombs, along with flares, leaflets and a parachute-support banner reading "Biko" were dropped into Eden Park from a light plane flying overhead. A New Zealand All Blacks player was felled by one of the flour bombs.
The effect of flour bombs is made worse by the inclusion of eggs, or containers of other liquid, making the removal of the resultant mixture difficult.