The special conditions for toy fireworks

Toy fireworks must be safe. There must therefore be a special way to convert firework compositions(explosives) which are generally quite dangerous, to make them safe for toys i.e. the compositions have to be divided and isolated. The principle is schematically shown in Fig.130. 

A composition can produce a great destructive force if it is set out in one place as in (A). But if it is divided into small amounts each 

In general, flames, hot air, fire dust sparks, sparks or shock waves help the propagation of fire or explosion. Four of the former only promote the burning of the compositions by direct contact, but the latter causes a detonation, even when the composition is fairly distant from the source. However in toy fireworks the item which produces a shock wave is limited to crackers. It is necessary therefore to draw a clear line between crackers and other items when handling toy fireworks. 

Compositions must be well covered by other material in order to protect them against flames, fire dust sparks or general kinds of sparks. In practice, the composition is wound with paper tape, twisted in pieces of paper tape or charged in small amounts into paper tubes. This plays an important role for the division and isolation of the composition. Some items like sparklers or Senk-Hanabi have exposed compositions with no cover but these compositions are quite insensitive to shock and friction and need no cover. Nevertheless they must be packed in groups with a small number in each pack. 

Crackers include such items as cracker ball, Christmas cracker. 

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