The old manufacturers held it to be impossible to reduce the ore in any other way than by means of charcoal of wood.
It was only when the wood in the neighbourhood of the ironworks had been almost entirely burnt up, that the manufacturers were driven to entertain the idea of using coal as a substitute; but more than a hundred years passed before the practice of smelting iron by its means became general.
The first who took out a patent for the purpose was one Simon Sturtevant, a German skilled in mining operations; the professed object of his invention being "to neale, melt, and worke all kind of metal oares, irons, and steeles with sea-coale, pit-coale, earth-coale, and brush fewell." The principal end of his invention, he states in his Treatise of Metallica,[2] is to save the consumption and waste of the woods and timber of the country; and, should his design succeed, he holds that it "will prove to be the best and most profitable business and invention that ever was known or invented in England these many yeares." He says he has already made trial of the process on a small scale, and is confident that it will prove equally successful on a large one.

Sturtevant was not very specific as to his process; but it incidentally appears to have been his purpose to reduce the coal by an imperfect combustion to the condition of coke, thereby ridding it of "those malignant proprieties which are averse to the nature of metallique substances." The subject was treated by him, as was customary in those days, as a great mystery, made still more mysterious by the multitude of learned words under which he undertook to describe his "Ignick Invention" All the operations of industry were then treated as secrets.

Each trade was a craft, and those who followed it were called craftsmen.

Even the common carpenter was a handicraftsman; and skilled artisans were "cunning men." But the higher branches of work were mysteries, the communication of which to others was carefully guarded by the regulations of the trades guilds.

Although the early patents are called specifications, they in reality specify nothing.
They are for the most part but a mere haze of words, from which very little definite information can be gleaned as to the processes patented.