Eric Twitty

Pretty interesting; by a consultant who specializes in mining history. One of the surprises for me was how long it took for explosives to be adopted by miners; while gunpowder dates to the 13th century and was known in Europe by 1267, the first recorded use in mining was in Hungary in 1627. This illustrates one of author Eric Twitty’s themes; miners are notoriously conservative and superstitious and it takes a long time to get them to adapt new technology. However, he also notes another potential explanation; safety fuse wasn’t invented until 1831. Prior to that touching off explosives involved a train of blasting powder, or a “squib” of powder twisted in paper and lit; both methods tended to be dangerous to the user.

A lot of the history of explosives in mining is actually the history of drilling holes in rock; Twitty discusses single jacking, double jacking, triple jacking, steam drills, compressed air drills, and various ways of employing them. Once you had a hole, you had to get the explosive into it; methods ranged from pouring in loose powder from a keg through home-made “cartridges” to factory packaged cartridges made from waterproof paper. Safety fuse revolutionized things here, too, since fuse burned at a measured rate, it was possible to cut fuses such that charges in the mining face went off in a specified order.

The introduction of new explosives again met with slow acceptances by miners familiar with blasting powder. Nitroglycerin was very powerful but also very shock sensitive, and some spectacular accidents led to railroads and shipping companies refusing it. The discovery that nitroglycerine would soak into various substances ranging from sawdust to clay resulted in dynamite, a powerful explosive that was much safer to handle than liquid nitroglycerin. Once again, miners tended to be conservative and resist it, sometimes deliberately misusing dynamite to demonstrate it was inferior to familiar blasting powder. To be fair, dynamite had some problems; most prominently it would freeze at a relatively high temperature (40° to 50°F) and frozen dynamite tended to be very unpredictable, sometimes more sensitive, sometimes less, sometimes releasing a lot of unpleasant gas when exploded. Various expedients to thaw dynamite were marketed but miners tended to improvise, sometime with spectacular results; needless to say, these were blamed on dynamite, rather than the imprudence (for example) of attempting to thaw it by stacking it in boxes in the boiler room.

Twitty notes that coal mining required different techniques; high explosives that nicely shattered hard rock for removal instead reduced coal to unsaleable fragments. The possible presence of explosive methane in coal mines also posed problems. Another application was open pit mining and quarrying, requiring specialized techniques; these used much larger drill holes and much more explosive (sometimes an initial hole was blasted to create a cavity at the bottom; then that was filled with explosive and blasted to create a larger cavity, then finally that was filled with a lot of explosives for the final blast.

Clear, well-written, and extensively illustrated. Twitty is mostly interested in historical mining so there’s little mention of the most modern techniques. One minor but annoying error is the consistent reference to “Hugh’s bits” rather than “Hughes bits” on drills. Well referenced, although most of the reference come from specialized mining and explosive journals; well indexed.… (plus d'informations)