Gunpowder

A simple pyrotechnic composition of gunpowder can be made with potassium nitrate (saltpeter) 75 grams, flaky carbon (charcoal from softwood best) 15 grams, and sulfur (brimstone) 10 grams, respectively, mixed in a low-speed non-sparking copper ball or lead ball static free rotary tumbler mixer until a uniform mix achieved. 

This dirty deflagrating gunpowder standard since about 1780, its combustion byproducts potassium & sulfur oxides from corrosive hydroxides that rust iron & steel barrel metals easily, meaning the users of black powder rifles have to clean & oil the bore & movement after firing the weapon repeatedly. Furthermore, smoke & soot emitted from the end of a barrel was a visual impairment, gave away the soldier's position & smell bad. 

Today, gunpowder still used in slate rock mining since it has lower brisance (shattering power) than other explosives commonly used in mining where fine rock fracturing desired, the lower deflagration explosion of gunpowder helps to cleave off the slate rock into sheets useful for expensive roofing & other masonry applications. In fireworks, slower burning carbon replaces charcoal in the mix, to make gunpowder based solid rocket motors for skyrockets & bottle rockets & to launch festival balls, mortars & other aerial fireworks. Gunpowder also used in cannon fuse & fireworks fuses, quick matches & in other cakes & firework assemblies and devices.  

Gunpowder also known as black powder, makes sense given the dark color of the final mix, mostly colored by the charcoal dust in the mixture. Gunpowder a granular mix of an oxidizer, typically potassium or sodium nitrate (KNO3 better, less hygroscopic), charcoal which provides fuel in the form of pyrolyzed cellulose, and sulfur, which also serves as a fuel while also a catalyst that lower the activation energy or temperature required to ignite the mixture, thereby also increasing the rate of combustion, especially in firearms where the chamber pressure can get to 50,000 PSI. The granules of modern gunpowder coated with graphite powder to reduce risk of electrostatic spark ignition accidents. Gunpowder for black powder rifles and cannons comes in F, FF, FFF, and FFFF grades, where F the coarsest or largest granules and FFFF a very fine powder.

Many compositions of gunpowder have varied throughout history, black powder used in mining for example does not work well in firearms, known as blasting powder, which is also typically made with the cheaper sodium nitrate, at mass percentages as low as 40%, 30% carbon & 30% sulfur respectively. Blasting powder was prone to absorbing moisture until 1857 when Lammot Du Pont found that tumbling gunpowder cakes & grains in graphite powder made them more hydrophobic or reducing the blasting mixture's ability to absorb moisture (known as DuPont "B" blasting powder). Coating gunpowder with graphite became an accepted manufacturing technique as early as 1839. 

In rocketry, slower burning gunpowder accelerates the rocket for a longer time, where faster burning gunpowder more ideal in flintlock, cap-lock, matchlock guns that need a higher burn rate to accelerate the projectile down the barrel. Slower burning gunpowder also used in black powder cannons. Gunpowder continues to be used in black rounds, burst charges, signal flares, in solid rocket motors, in fireworks for lifting shells & for other special effects. 

Combustion of gunpowder turns less than half the mass into gases, producing an abundance of PM or particulate matter, which is typically ejected from the muzzle of barrels, wasting chemical energy power, fouling the air nearby & making a visual signal with smoke fog, all while depositing corrosion promoting soot in the barrel, which jams weapons, especially high fire rate automatic weapons. 

With 3 megajoules per kilogram, gunpowder less energy dense than TNT with 4.7 MJ/kg and gasoline 10.4 MJ/ kg respectively. Modern smokeless powders have much better energy density, cleaner burn characteristics, and enable higher energy case loading, important with higher mass bullets in these popular large caliber handguns, and super powerful rifle calibers. Gunpowder was largest replaced by smokeless powders, starting in the 1950's.