Introduced in the 1810s and used as plates for engraving and mezzotint. Steel was much more durable than copper and therefore virtually unlimited editions could be produced from steel plates, whereas copper tended to wear out very quickly. However, steel was much tougher to work than copper and manual engraving of a design with a graver was virtually impossible. Accordingly, most ‘engravings’ produced in this manner were in fact etched. With the introduction of steel-facing in 1857 it was possible to combine the malleability of copper and the durability of steel.