A squib is a small explosive device used to generate a mechanical force or visual effect. Squibs usually resemble a small stick of dynamite or layered fabric sheet, with each style containing a small quantity of explosive substance along with a central detonator. Squibs can either be detonated via a traditional slow-burning fuse – like the one shown in the image below – or by a wired connection to a remote electronic trigger, the latter being more common today due to increased safety standards.
Typical uses of squibs include separating different materials – for example, in coal mines, where small detonations can break away valuable coal from worthless rock, and as a controllable pyrotechnic. Squibs can simulate explosive effects for theatre and film productions without the need to use high-powered explosives, which are a lot more dangerous and expensive.
Historically, squibs were originally constructed from tubes of parchment and were filled with black powder. These primitive squibs did not have the insulating, water-resistant coating that they do today and, as such, if they got wet they would not function. This is where the common phrase ‘damp squib’ originates and why it is used to indicate that something has not worked correctly or to its maximum potential.