Until 1742, producing steel was a difficult task. The quality of the steel was often unreliable. The steel was made by heating iron bars which were covered in charcoal. The heating was continued for up to a week. The material produced was called blister steel.
Blister steel was then turned into shear steel by wrapping blister steel bars up in a bundle and then heating them again before forging the bundle. The heat and the action of the forge hammer welded the rods together as they were hammered to the size required. This shear steel was used to make razors, files, knives, swords and the other steel items for which Sheffield became famous.
No more than about 200 tons of steel were produced each year in Sheffield, using this process.
Benjamin Huntsman's crucible steel process changed all that. He was the first person to cast steel ingots. The process produced uniform high quality steel in reasonably large quantities,
M. Le Play, Professor of Metallurgy at the Royal School of Mines of France, wrote in 1846 that Huntsman's memorable discovery advanced the steel manufactures of Sheffield to the first rank, and powerfully contributed to the establishment of the industrial and commercial supremacy of Great Britain.
Within 100 years of the invention of the process, Sheffield was producing 20000 tons of crucible steel a year. This was 40% of the total amount of steel produced in Europe at this time.