The reaction that causes the whistling effect is
the layer-to-layer oscillating burn of the firmly
compressed composition with the containment tube acting
much like a resonator.
Be careful, this is a high energy mixture that can
explode with friction/impact. Grind the Potassium
Perchlorate ALONE in a mortar & pestle until it
is a very fine powder (unless it's that way already).
Do the same to the Sodium Benzoate unless it is already
as fine as Talcum Powder. Note that the Sodium Benzoate
must be VERY fine, and mixed VERY well with the Potassium
Perchlorate for this mixture to work properly. Pass
the mixture through a screen several times to mix
the two together. It is important that this formula
be mixed very well and be in a fine powered state.
Pour the Whistle Mix into a zip-loc plastic baggie,
seal it, and shake it back & forth just to make
sure the composition is well mixed.
Don't ever grind the two ingredients together as the
mixture may explode. Never grind, pound, or subject
this mixture to friction as it may explode.
INSTRUCTIONS
To make a Whistle, seal off one end of a heavy wall
cardboard tube with Plaster of Paris or a quantity
of heat glue, or some rocket nozzle mix. The tube should
be heavy walled cardboard and the length should be 3
times the inside diameter.
If the tube is too long, results will be poor.
The larger the diameter, the louder and less
pitch the whistle will be.
Experimenting with different tube diameters and
lengths will reveal a variety of pitch and tone. Tubes
with a 3/8” to 5/8” inside diameter work well. Using
a wooden dowel the same diameter as the inside of the
tube, press small increments of Whistle Mix into the
tube. Press hard to pack it in, but do not bang on the
dowel. Fill the tube only 1/2 full (whistles need a
lot of empty space in the tube). Stick in a length
of Visco Safety Fuse and make sure it touches the powder
inside. Push the tube into the ground so it stays
put, stand back and light the fuse.
