FIREWORKS

288 Fireworks Principles and Practice
an explosion. This is overcome by charging the first increment with a
slow composition.
The so-called display "Fix" are 12-16 mm inside diameter and 25
cm long. They are choked to half a diameter and charged by hand or
pressed in about eight increments. The compositions are quite fierce
for they are required to produce two or three feet of concentrated fire
for set piece pattern work. The following compositions are used for
this purpose:
A B C
Weight Weight Weight
(%) (%) (%)
Meal gunpowder 84 73 64
Charcoal 150 mesh 16 — —
Potassium nitrate — — 8
Sulphur — — 8
Iron 60 mesh — 27 20
Fountains of 18 mm to 75 mm inside diameter require less fierce
mixtures but if they are not strong enough they will "deteriorate'' lower
down the tube owing to blockage from dross. These compositions are
usually cheaper because they contain less gunpowder, but they are
invariably dirty because finely powdered materials are required. The
following mixtures are fairly uncomplicated
A B C D
Weight Weight Weight Weight
(%) (%) (%) (%)
Potassium nitrate 150 mesh 72 40 44 27
Sulphur 8 8 9 14
Charcoal 40/100 mesh 16 — — 9
Charcoal 28 mesh 4 — — —
Charcoal 150 mesh — 8 8 —
Meal gunpowder — 16 9 40
Coated iron 20 mesh — 24 30 —
Titanium 40 mesh — — — 10
Aluminum flitter 10/30 mesh — 4 — —
The old English "Flower Pot" is produced from a combination of red
orpiment and lampblack. The burning is very drossy with the result
that bits of dross are forced into the cool air where they sparkle with
their characteristic golden coruscations. The following compositions
are typical, but it needs to be emphasized that only certain types of gas
black will function correctly and the material has to be chosen by trial
and error.
An excellent article in Pyrotechnica XVII well illustrates the prob-