Steel engraving replaced copper as the dominant intaglio method in the early 19th century because hardened steel plates could hold finer lines and survive far longer press runs. The result was a generation of scientific and natural history illustration with extraordinary precision: feathers, scales, anatomical structures, and shell formations rendered with a delicacy that earlier techniques couldn't sustain. Much of the most ambitious work appeared in encyclopedic publishing projects of the 1820s–1840s, when European naturalists were racing to document the natural world in print.