A number of members have asked me about different compounds to use as break for small shells. One of the most versatile breaks is whistle mix. Whistle mix is a mixture of 70/30% (by weight) Potassium Perchlorate and Sodium Benzoate (or Potassium Benzoate), respectively. Older formulas also use Sodium Salicylate as a fuel, but this is less desirable as it is more hygroscopic, and has a lower ignition point than the Benzoate fuels. I mostly use Sodium Benzoate as a fuel as it is more readily available and is the least expensive. This makes a very powerful and useful break powder, for use loose or on rice hulls.

Manufacture: It is vitally important to have a very intimate mixture between the fuel and the oxidizer, and it is equally as important to make sure that the ingredients arew reduced to a small particle size before mixture. When used strictly as a whistle, the mix will not function if the components are not properly prepared before mixture.

The Sodium Benzoate is very sticky and is hard to simply screen for size. To insure that it is fine enough, I put about a cup of it (with a little cabosil) in a standard kitchen blender and then shake the blender and motor up and down while running. This will make the fuel 'fluff-up' quite a bit. (Note: I use this blender method to reduce all of my fuels and salts which are water soluble and not impact or friction sensitive, such as Potassium Nitrate, etc.) When I have enough fuel I then weigh out the Potassium Perchlorate and screen it through a 100 (or finer) mesh screen until it will flow through the screen easily.

Once the ingredients are ready and weighed, I combine them by carefully 'blanket-rolling' them together on a large piece of kraft or newspaper. It is important to mix this way and generally treat the mixture just like flash: try a half full 3" tube of the mix as a ground salute sometime.

After mixing, try some rammed in a small tube to see if it whistles. If it does, it's ready!

Use: Whistle mix may be used as a break charge in shells either loose or on rice hulls. It's use loose is primarily in plastic shells, such as Kosanke's 'RAP' shells. The stars and whistle mix are simply put in the shell and mixed together so that the whistle mix coats the stars evenly: usually about a level tablespoon in a 3" and a heaping tablespoon in a 4". In a traditional canister-type pasted-up shell, whistle mix on rice hulls is needed. To coat the rice hulls, cover them in boiling or very hot water and let stand for a few minutes. Drain the rice hulls and put them in a 5 gallon plastic bucket. While turning the bucket, and perhaps stirring with a wooden stick, add the whistle mix until you get an even, light coating on the rice hulls. Then spread the coated hulls out on a screen to dry. No binder is needed as the mix is quite sticky (often binders such as dextrin are needed to get other compounds such as flash to stick to the hulls).

I also use this for small whistles. If you are ramming whistles with this mix you will find that you need to leave a space in the ignition end at least as long as the inside diameter of the tube in order for it to whistle upon ignition. A progressive burn taper of about 90 degrees is also helpful to the whistle effect. Nozzles are not necessary or desirable. I also add up to an additional 10% by weight of 40 mesh Titanium flake ( Suissman: available from Kosanke) to the mix for a whistle with a spark tail. This is a nice effect for ground displays or as an addition to a shell.

Other Considerations: Whistle mix is really at it's best when used fresh: mix up just what you need for break or whistles and don't leave loose mix hanging around. The loose mix just starts to suck up moisture and it's just as migratory and as dangerous to store as loose flash.

I hope this is helpful, and I welcome any comments or questions.

Mike Stoumen