The Chemistry of Powder and Explosives - Sciencemadness Dot Org

GERBS 89
Gerbs
Gerbs produce jets of ornamental and brilliant fire and are
used in set pieces. They are rammed or pressed like rockets, on a
short nipple instead of a long spindle, and have only a slight
depression within the choke, not a long central cavity. They are
choked to about one-third the diameter of the tube. The simplest
gerbs contain only a modified black powder mixture, say meal
powder 4 parts, saltpeter 2, sulfur 1, and charcoal dust 1 or
mixed charcoal 2, and arc used occasionally for contrast in
elaborate set pieces. Similar compontion is used for the starting
fire of steel gerbs which are more difficult to ignite. If antimony
siilfide is used in place of charcoal, as in the mixtures:
Meal powder
Saltpeter
Sulfur
Antimony sulfide.
2
. 8
3 1
the gerbs yield compact whitish flames and are used in star and
floral designs. Gold gerbs appropriately arranged produce the
sunburst effect. Colored gerbs are made by adding small cut
stars. In loading the tube, a scoopful of composition is introduced
and rammed down, then a few stars, then more composition
which is rammed down, and so on. Care must be exercised that
no stars containing chlorate are used with compositions which
contain sulfur, for an explosion might occur when the charge is
rammed. The following compositions are typical. The steel filings
Meal powder .. .
Potassium nitrate .
Sulfur ..
Fine charcoal
Steel filings
Stars..
Sodium oxalate
Antimony sulfide
Aluminum .
Dextrin
6
2 11
1
Steel
4
1
2
3
8
4
?
Colored
Steel
8
7
2
5
5
Gold
40
6
8
4
Colored
Gold
40
5
6 9
4