Fountains charcoal

Charcoal is used in excess because the decomposition of the extra charcoal is endothermic, the overall effect being to lower the exothermicity of the fountain composition and so reduce the burning rate. However, the main advantage in using extra charcoal is that a reducing atmosphere is produced within the fountain such that the possible reaction of the emitter prior to ejection is greatly reduced. 

More exotic effects call for more exotic materials, and considerable effort has gone into formulating compositions that are both spectacular in effect and safe to produce and handle. Thus a 30 mm fountain might contain mealed (or hue) gunpowder, potassium nitrate, sulfur, charcoal, antimony trisulhde, barium nitrate, hue aluminium and flitter aluminium with a dextrin binder. This composition is certainly a good deal more complicated than that used for sparklers but is relatively safe to produce and gives a good burst of white sparks. 

The charcoal, or rather the coated charcoal, contributes to the fountain effect as does the gunpowder and aluminium by processes such as those described above. The flitter aluminium has a rather coarser particle structure than does the fine aluminium so that sparks from the former are longer lived and can survive a greater drop-height. Antimony trisulfide is commonly used to enhance the glittering effect in a series of chemical reactions with the gunpowder and aluminium. 

Some fountain compositions tend to be oxidant-rich due to the presence of excess potassium nitrate or sometimes various oxalates. The reason for this is to reduce the burning rate and/or to enhance the visual effects. Certainly if gunpowder is considered to be a mixture of fuels (charcoal and sulfur) and oxidant (potassium nitrate) then the maximum rate of burning should coincide with a slightly under-oxidised system. The burning rate is therefore reduced by adding excess nitrate to the system. 

The charcoal, or rather the coated charcoal, contributes to the fountain effect as does the gunpowder and aluminium by processes such as those described above. The flitter aluminium has a rather coarser... 

---