Copper and Steel Engraving
A copper engraving is made by incising lines on a copper plate using a sharp tool called a graver or burin.
These lines or grooves can be of varying depths which will then hold varying amounts of ink, the resulting printed line being lighter or darker as required.
The image is engraved in reverse and when ready for printing ink is rolled over the surface of the plate and then carefully wiped from the surface so that ink remains only in the incised lines.
In order for an image to be successfully printed great pressure must be applied to the paper and the engraved plate. This is achieved by first of all dampening the paper before positioning on the plate.
On top of this is laid a wool blanket and the plate, paper and blanket are then rolled between two large cylinders, the resulting pressure forcing the damp paper into the grooves in the plate in order to take up the ink and hence create the image.
One of the qualities of the copper plate is that the material is quite soft and as a result wears down quickly with repeated pressings so that the plate has to be re-engraved or else a new plate made.
However, the 1820s saw the development of steel plates for engraving. The method for producing a steel engraving is essentially the same as that for copper. The main difference is that steel is a much harder material and so is more resistant to wear.
Also, because it is harder it is possible to engrave much finer lines and hence much greater detail than is possible with copper.