Name: 6:1:1
| percent | parts | component |
|---|---|---|
| 75.00% | 6 | Potassium Nitrate |
| 12.50% | 1 | Charcoal (airfloat) |
| 12.50% | 1 | Sulfur |
Chemicals are pre-ground very fine, then screened together well. May be milled into meal which is almost identical in performance to conventional 15:3:2 black powder meal.
This is a very old BP composition. It is still widely used in cheap Chinese cracker and rocket devices, fuses, spoulettes, and as a basis for gerbs and drivers.
It performs quite well as a propellant, even as greenmix, and is relatively tolerant of poor potassium nitrate purity (hence its popularity in historic texts). The charcoal is best increased somewhat if it is impure. Both of these behaviours stem from its slight over-oxidisation with practical charcoals:
It is derived from the naive stoichiometric equation:
2(KNO3) + 3(C) + S => K2S + N2 + 3(CO2)
Which gives molar mass ratios (to two significant figures):
63 Potassium Nitrate
11 Charcoal
10 Sulfur
Or when shown as percentages approximately 75:13:12 which can been seen is quite similar to conventional 75:15:10 BP. The difference is mainly the need for excess charcoal to make up for its relative impurity and a slight over-oxidisation to hasten the reaction and make up for oxygen loss as the reaction proceeds and the reactants expand.
Of course black powder's true reaction is quite a bit more complex (and pressure dependant) so all this is approximation at best. Even the "gold standard" 15:3:2 ratio is generally not optimal for practical charcoals. With hemp or willow charcoal you won't notice the difference between 6:1:1 and 15:3:2, but with poor quality charcoals 6:2:1 often works better than you might expect.