I would like to begin this article by thanking and crediting my instructors. Doc Barr introduced me to strobe rockets years ago. Steve LaDuke walked me through my first attempts at this pyrotechnic formula. Without them, this article could not have been written.
White strobe rocket pyrotechnic formula (in parts by weight):
Metal (see below)
Additional, by weight, Potassium Dichromate
Nitrocellulose as a binder
Some of the firework chemicals require prior preparation. The ammonium perchlorate is ball milled for 2 hours with a hard milling medium, until it is of powdered, chalk-like consistency. The magnesium-aluminum (magnalium) metal I use is -200 mesh, and I ball mill 300 grams at a time for 3 hours with steel ball bearings as the milling medium. The potassium dichromate is ball milled for 18 hours to a very fine dust.
The firework chemicals used pose both inhalation and toxicity hazards and appropriate safety equipment is to be used.
The pyrotechnic formula I like best uses, as the metal component, a mix of 23.5% ball milled 50:50 -200-mesh magnalium metal and 1.5% 60-100-mesh magnesium flake. Steve LaDuke and I have used a pyrotechnic formula with 25% -200-mesh magnalium without ball milling it at all. It gives a slower strobe rate. The first formula yields a rapid strobe with a loud popping sound. Fred Partin has also used many strobe rocket pyrotechnic formulas of this and other colors and may be consulted as well for variations on this theme. For a very slow strobe, of no use in strobe rockets where thrust is desired, you may use 25% 30-mesh magnalium.
The binder is standard 10% nitrocellulose (NC) lacquer diluted with acetone. I use 1 part NC lacquer to 3 parts acetone. The amount used in the mix is not critical. Doc Barr has even made strobe rockets with this formula using no NC binder.
Start by sifting the ammonium perchlorate, metal, and potassium dichromate twice through a 40-mesh screen. Then add the barium sulfate and sieve the entire mix through a 20-mesh screen twice. To avoid corrosion, use stainless steel sieves.
Take the composition and add enough diluted NC lacquer to just barely moisten it. You should be able to squeeze it and have it hold its shape. One kilo utilizes approximately 4 to 5 ounces of diluted NC lacquer.
Granulate the moistened composition through a screen of about 20 mesh or coarser using a 1.5-inch dowel section as a pestle. Dry the mixture thoroughly, at least 12 hours. It is now ready for use in making strobe rockets.
The mixture has a long shelf life. I have used batches that have been stored for over three years. As with any strobe rocket compositions, use caution at all times, and above all else, be safe.
Note: No clay nozzle is needed. For a two-pound strobe rocket, press whistle composition for the first 1 3/8 inches and finish with strobe rocket mix to 1/8th to 1/4 inch above the spindle top. Do not exceed 1/4 inch above the top of the spindle. Strobe burns very slowly; if you press too much strobe rocket composition above the spindle, your strobe rocket will burn all the way to the ground. Top off the strobe rocket with about one inch of pressed whistle composition. Confine the strobe rocket tube in a sleeve when pressing.
NEVER RAM/HAMMER WHISTLE MIX! ALWAYS USE A PRESS. Pressures? If you are using a 12-ton hydraulic press, your pressures should be between 2,000 and 2,500 PSI on the gauge.