**** Ulrich Bretscher's Black Powder Page ****
The Recipe for Black Powder
As is generally known to many people, black powder is a mixture of saltpeter, charcoal and sulfur. To disappoint all of you who think, in the following paper I'm going to give away an optimum recipe with the best possible performance, I state here once and for all: The mixture of the three ingredients is of little importance. It is the method of making the charcoal that counts, as I will prove with this chapter.
But back to the black powder recipe: You can change it over a wide range, and hardly notice any difference between performances. That explains why most of the historic recipes differ significantly. On the other hand, it is hard to find a historic recipe on how to char the coal, since that usually was a state secret.
By the way, even a mixture of saltpeter and charcoal without sulfur explodes remarkably well. However, a mixture of saltpeter and sulfur, without charcoal, doesn't burn at all. The latter fact puzzled the chemists throughout the centuries, because sulfur alone burns pretty well and saltpeter generally accelerates all sorts of fires.(Look this movie)
Note: Charcoal does not consist of pure carbon (C) as most authors purport. Such a pure charcoal would require a charring temperature of at least 1,500 °C! And a black powder mixed with it would probably burn like the head of a matchstick, at best.
As I'm explaining in my charcoal chapter, the formula of charcoal may be best described as C7H4O. With this and the following chemical equations we'll see why there won't be an explicit, best mixture of black powder:
Depending on the portion of charcoal, its carbon produces alternatively carbon dioxide or carbon monoxide or a mix of both. To these you'll have to add the water vapor plus nitrogen, released from the saltpeter. So the sum of all the gases is nearly the same on all recipes. Indeed, the following three dimensional graph of the performance of different black powder recipes reveals a flat top over wide range of recipes.
A recipe without sulfur yields only little less energy (Joule/g). But its advantage lies in its little smoke produced. Its fog then consists of potassium carbonate (potash). Unfortunately its ignition temperature is 100 °C higher than usual. For cap lock arms that is no problem, but it is a nuisance to flint and match lock sportsmen.
Here is the chemical equation for a regular black powder containing sulfur:
Reasonable recipes for mixing blackpowder are;
A good standard black powder:..100 parts saltpeter + 18 parts coal + 16 parts sulfur
The muzzle energy was determined by the measurement of the bullet velocity, one meter ahead of the muzzle of a three band Enfield rifle, cal. 58 (14.7 mm) and a patched round ball of 17.3 g lead. The velocity was measured by a commercially available chronograph. With each recipe there were three shots fired and from these the median was taken. The load was exactly 2.00 g black powder.
Then the muzzle energy was calculated as:
Contemplating the diagram in Fig. 1, you might ask yourself, why on earth did our ancestors take the trouble to add sulfur at all? That idea first occured to the Swiss artillery in 1875, when "smokeless black powder" was tested. Firing salvos out of a fortification soon made the enemy invisible, due to the heavy smoke of the hefty loads of cannons. Since those tests were done on the eve of the "white-powder" era, the findings soon became obsolete.
A sulfur-free black powder yields only little smoke. When it is used in a rifle, you see only a faint fog. When fired by a percussion rifle, the ignition poses no problems. From by flint lock, you will get lots of misfires.
So I tested the ignition temperature of (homemade) black powders by increasing the temperature in a laboratory oven in increments of 10°C and found the purpose of sulfur in the black powder mixture:
p = parts