The mixture is suspended in water with some gum arabic or similar binder and deposited in drops, each containing a few milligrams of explosive, to dry between layers of paper backing.
[6] Armstrong's mixture has been used in thrown impact-detonated improvised explosive devices, made simply by loading it into hollow balls.
[1][better source needed] Armstrong's mixture is both very sensitive and very explosive, a dangerous combination that limits its practical use to toy caps.
If the pH is not made neutral, phosphoric acids that may have been generated by oxidized phosphorus on contact with the water could cause it to deteriorate while slowly drying.
A store containing some six to eight million paper caps, totaling about 64 kilograms of explosive mass, caught fire and exploded, killing 14 and injuring 16 more.