Following on from the ‘Idiom’ story in The Mover on a damp squib, December 2011, here’s the answer.

David Cameron described the recent public sector strike as a ‘damp squib’.  Whether it was or not, what exactly is a squib and why does it matter if it gets damp?  

A squib is a miniature explosive device used in a wide range of industries, from special effects to military applications. A squib generally consists of a small tube filled with an explosive substance, with a detonator running through the length of its core, similar to a stick of dynamite. Also similar to dynamite, the detonator can be a slow-burning fuse, or as is more common today, a wire connected to a remote electronic trigger.  Squibs range in size, anywhere from 2 to 15 millimetres in diameter. Squibs can be used for generating mechanical force, or to provide pyrotechnic effects for both film and live theatrics. Squibs can be used for shattering or propelling a variety of materials.

In the North American film industry, the term squib is often used to refer to various electric matches and detonators (used as initiators to trigger larger pyrotechnics). Squibs are generally (but not always) the main explosive element in an effect, and as such are regularly used as “bullet hits”.

Origin of the phrase "damp squib"

While most modern squibs used by professionals are insulated from moisture, older uninsulated squibs needed to be kept dry in order to ignite, thus a ‘damp squib’ was literally one that failed to perform because it got wet. The phrase has since come into general use to mean anything that fails to meet expectations.