Coal came into wide use in the late 1590s in the United Kingdom after the island nation was widely deforested and a ban was placed on the harvesting of wood by
Charles I of England, so that forests could be used solely by the
Royal Navy. A newly emergent
middle class increasingly demanded
glass for windows, and the glass-making industry relied heavily on
charcoal for fuel. With charcoal no longer available, the glass industry turned to coal. Demand for coal also increased after the invention of the
reverberatory furnace and the development of methods for casting iron objects such as cannons. Coal is often mixed with impurities such as rock,
slate,
sulfur, ash (or "bone"),
clay, or soil. The second function of a coal breaker was to remove as many impurities as economically desirable and technologically feasible, and then grade the coal based on the percent of impurities remaining. The smaller lumps of coal were considered non-marketable and left in the mine. Beginning about 1830, surface processing of coal in the US began concurrently with various canal projects in the Eastern Seaboard. These developments lagged behind that of Great Britain, better matching the timing of similar developments in Continental Europe. Great Britain, with its heavily deforested landscapes, simply had to find economic alternatives sooner, stimulating coal, iron, and machine developments leading ultimately to railroads and the infant
industrial chemicals industries of the 1860s. Lumps of coal were placed on plates of perforated
cast iron. "Breakers" would hammer on the coal until it was in pieces small enough to fall through the holes. A second screen caught the coal, and it was shaken, by hand, animal, steam, or water power to remove the unmarketable smaller lumps. This "broken and screened" coal was worth much more than "broken" coal or lump coal. ==Use of breaker boys==