The main cause of accidents was premature explosion. The chemical reaction that generated gas and heat from the decomposition of black powder was best activated by a spark or flame but getting close enough to the charge to apply a flame and escape quickly enough to avoid injury was a distinct skill, as noted earlier. Premature explosions could also occur accidentally.
In 1745, an electric spark was used by Dr. Watson of the Royal Society in England to explode black powder, and, in 1750, Benjamin Franklin improved his procedure by compressing the powder into a case (DuPont 1980). This could be done from a distance, which improved safety, and electric firing was tested successfully in Austria in 1804 and was being used in England by 1835 (McAdam and Westwater 1958). But electric firing was a step into the unknown that had to be taken cautiously with explosives. The main advance in igniting black powder is attributed to William Bickford in Cornwall in 1831 who placed a thin, slow-burning core of powder in a cable of jute and string and applied a flame at one end. The flame took some time to reach the explosive and this gave the shot-firer an opportunity to find safety. Within a few years the cable was coated with varnish to make it waterproof. The safety fuse reduced accidents by 90%. The fuse was continually improved by the use of better materials and these increased the safety factor still further. In 1958, fuses were burning reliably at a speed of 90 sec/m with an accuracy claimed to be 10%. It was far removed from the fire-and-run technique of 100 years previously.