Whistle - Benzoate Whistle


Name: Benzoate Whistle
Source: Selšuk Íztap, Doc Barr, John Steinberg, et al


percent parts component
74.15% 76 Potassium Perchlorate
22.44% 23 Sodium Benzoate
2.44% 2.5 Petroleum Jelly
0.98% 1 Iron (III) Oxide

Required Mass


Pre-screen the Potassium Perchlorate several times. Screen the Iron Oxide and Sodium Benzoate together well.

Dissolve Petroleum Jelly in a small quantity of Petroleum Spirits (or other suitable solvent) warming gently on a water bath, dilute sufficiently to allow full wetting the combined quantity of composition.

Mix solution with Sodium Benzoate and Iron Oxide mixture and stir to wet completely. Add Potassium Perchlorate and mix very well, adding extra solvent if required.

Force through a sieve at least five times to achieve a completely homogeneous pink dough. Use a waterbath if required to drive off excess solvent and achieve a crumbly consistency, screen again and spread out on paper to allow the solvent to evaporate completely.


Burn Rate: 7.4 - 7.6 mm/s

Despite the stabilizer it is still a rather sensitive composition. It should be pressed, not rammed, into tubes.

Some say drying on paper causes too much of the stabilizer to be wicked out and lost leaving an overly sensitive composition, but I haven't experienced this problem in practice. However I use kitchen wrap rather than kraft which tends to be more 'hairy' and absorbent.

It is a usable nozzleless rocket propellant, a short core (about 3-4 IDs of the case long) is useful, but too large and the rocket may explode.

Sodium Salicylate can replace the Sodium Benzoate one-for-one for a more powerful composition, especially for rocket propellant. Using Potassium Benzoate is helpful in high humidity environments, but it is more expensive.

The mixing has to be excellent, especially for Benzoate whistle, any specks of white visible means you need to wet it through again with the solvent and rub it through a sieve over and over until it is homogeneous.