The era of explosives started with the invention of fireworks some time in the first millennium AD. It is believed that fireworks started in China, one version being that they were created by the residents’ habit of building wood fires on top of saltpeter rocks. The heat caused chemical decomposition of the saltpeter, and this generated copious quantities of gas and heat—a process called deflagration. The gas would have discharged particles from the burning saltpeter that glowed red hot, and this would have created a spectacular display. Addition of sulfur was found to improve the firing. These accidental fireworks led to the formulation of a saltpeter-carbon-sulfur mixture, which could be used for formal fireworks and for signals. Military use followed in the 8th century when a product made of 1 lb of sulfur, 2 lb of charcoal, and 6 lb of saltpeter was used for “…launching fire upon an enemy” (McAdam and Westwater 1958), but it was the 13th century before the great potential of controlled deflagration for launching missiles for military use was recognized and the 14th century before it was seriously used. Then explosives were developed for weapons and later for rock breakage, which changed the course of civilization.
“Arabs are said to have invented the first real gun. In 1304 they reinforced a bamboo tube with iron and shot from it an arrow propelled by suddenly expanding gases released by ignited gunpowder” (Wilkinson 1966). The early formula for gunpowder was 10 parts saltpeter, 2 parts charcoal, and 1.5 parts sulfur (Eissler 1897)—a mixture that did not change much for 500 years. But it was not only the Arabs who were interested in gunpowder and guns; in Europe monks also worked on saltpeter as part of their efforts to build industries for their monasteries. Roger Bacon, an English Franciscan friar, published a formula for gunpowder in the 1240s which was similar to the Arab formula, and Berthold Schwartz in Germany, a monk who was probably in the Augustinian order, invented a gun about 1380 (Drinker 1888). Schwartz was “.credited with seeing the possibilities of developing the magical explosive as a propellant to hurl balls from cannons, the first of which he is said to have constructed” (Wilkinson 1966).
The military use of gunpowder had its critics. In the early 17th century, Francis Thy — bourel, the French poet, mathematician, and physicist, reportedly wrote an epitaph for Schwartz: “Here lies the remains of Berthold the Black, the most abominable of inhumans who by his invention has brought misery to the rest of humanity. Hence the term black powder was coined” (Atlas Powder Company 1987).
Military effectiveness has always been a powerful argument for developing better technology, and by 1520 black powder was being used in warfare to supplement traditional weapons such as the sword, ax, and battering ram. Mining skills were highly valued in armies at that time because of the importance of excavations during sieges, but even then mine owners were hesitant to use blasting for more than 100 years. Perhaps the reason was that explosives were still unsafe, a fact recognized by an edict issued by King James I in 1623 that prohibited the sale of defective powder and required all gunpowder to be approved and marked.
Despite these problems black powder was not to be denied. It was widely used in Hungary by 1642, and by 1687 it was being used in tin mines in Cornwall and at other mining and construction sites. At that time blast holes were 50-60 mm in diameter, 1 m deep, and took 1 kg of powder (Drinker 1888). C. G.W. Lock wrote a succinct comment in 1889 on the long-term effects of the introduction of blasting to mining:
The all-conquering Romans drove his slaves and prisoners by regiments to toil in the gold mines of Hungary, and miles of tunnels may yet be seen there carved in the solid porphyry by hammer and chisel, the mines being worked to this day.
What the ancient Roman did by forced labour the Anglo-Saxon does now by the aid of steam, explosives and hydraulic power. (Lock 1889)
Safety problems with using small amounts of defective powder in guns were bad enough, but the problems were much greater with the large amounts required to break a mass of rock. But the potential advantages for breaking rock were known to be great, and on February 8, 1627, blasting was first used in an underground mine. Caspar Weindl, a miner from Tyrol, gave a demonstration of rock blasting at the Royal Mines of Schemnitz at Ober-biberstollen in Hungary, which had a long tradition of mining dating back to Roman times. The blast was successful but “Powder for blasting did not become common for a long time thereafter for several reasons: boring implements were crude, mining methods were unsafe, and the cost of explosives was high” (Wilkinson 1966).
The value of black powder in engineering was that detonating it in a rock mass generated sufficient gas to heave boulders from the mass, provided the rock had existing fractures, although it was less useful for rocks without fractures. This enabled men to break boulders into pebbles at much higher rates than if the boulders were pried from the rock mass by hand. It tended to restore the balance between the rates at which rock could be mined and milled, which had been altered when water-powered stamp mills were introduced 100 years previously. In time it probably moved the bottleneck in the production of metallic minerals back to the mill. The black powder era for ore blasting lasted for 250 years until the rise of dynamite. During this time size-reduction processes for ores involved
■ Black powder for the initial breakage of rock at the face
■ Hand breaking the pebbles and boulders from the explosion
■ Mechanical breakage of the finer fragments from blasting and hand breakage using stamp mills driven by water wheels
The value of black powder was such that it brought a seminal change to rock breakage technology and reduced greatly the terrible labor of manual mining. The tragedy of black powder was the cost of human life from the high rate of fatal accidents, and this cost had to be reduced.