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A gerb is a type of firework which produces a jet of sparks, usually lasting between 15 and 60 seconds. It is a thick-walled tube filled with pyrotechnic composition and possessing a choke, which is a narrowing in the tube. Gerbs are often referred to as 'fountains'. Sometimes a small charge of black powder is added to the bottom of a gerb to make it finish with a bang: this charge is known as the 'bounce'. These are commonly used at sporting events. Gerbs intended for use indoors near a proximate audience, such as at a rock concert, typically have shorter durations (from 1/8 to 30 seconds) and heights (4 to 50 feet). Gerbs are usually measured in terms of time and height. For example, a 4x4 burns for 4 seconds at a height of 4 feet. Eric Newby's book ''The Last Grain Race'' (chapter two Mountstewart) contains a 1938 reference to what appears to be the original gerb - in effect a mortar bomb fired from a mortar. ==External links== * (Fountain ) article at PyroGuide wiki 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gerb (pyrotechnic)」の詳細全文を読む スポンサード リンク
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