By the way, the charcoal does not actually react when gunpowder oxidizes. It simply serves as a medium to sustain the reaction. The sulfur actually oxidizes to sulfur dioxide and hydrogen sulfide, but it too provides a slow-burning combustible that sustains the oxidation of the KNO3, which is the primary fulminating ingredient.
One of the best things -- or the worst -- my parents ever did was buying me that chemistry set ...
Mom said that when she was young they made their own soap using this ingredient/method. (she's 85)