Printmaking is generally divided into three main categories or processes: relief, intaglio (of which etching is one type), and planographic.

Relief printing is the oldest, dating back to at least ninth-century China. In relief processes the background of the design is cut away, leaving the design on the surface of the block or plate. When the block is inked, only the surface receives the ink, which is transferred onto the paper by pressure from a printing press.

In intaglio processes such as engraving and etching, the design is made below the surface of the plate through a series of grooves made either with tools, or with a combination of tools and acid. In order to affect transfer from the plate to the paper, a special press, capable of exerting considerably more pressure than a regular printing press, is employed.

Planographic processes, which were not invented until the late eighteenth century, are based on the mutual rejection of grease and water. The design is drawn directly onto the surface of the plate with a grease pencil and then the plate is dampened before printing ink is applied. Only those parts that are greasy accept the ink. Transfer from plate to paper is made by the pressure of a special press.

The Intaglio Process with George Hawken

Two Plate Printing with George Hawken

Lesson 1 - Applying the Hard Ground

Lesson 2 - Drawing on a Hard Ground Plate

Lesson 3 - Etching the Plate

Lesson 4 - Applying a Soft Ground

Lesson 5 - Reworking the Hard Ground

Lesson 6 - Non-Acid Techniques, Drypoint and Roulette

Hollar was a master of the art of etching, an intaglio technique that was not developed until the beginning of the sixteenth century, as a less laborious way of achieving an image on a copper plate. Previous to the introduction of etching the design was incised directly into the surface of the plate with a burin or other sharp tool, that removes a thin sliver of metal shaving from the copper plate. In etching, the design is produced through the action of acid or other mordant. The design is drawn with a needle that penetrates the acid-resistant wax or resin coating previously applied to the plate. Then the plate is immersed in a bath of acid, which bites into those parts exposed by the needle. Deeper lines are produced by re-immersion in the acid, after lines which are not to be deepened have been stopped out with acid-resistant varnish.

Hollar exploited the technique of etching to its fullest, recording even the tiniest details with great economy and clarity. He was able to portray complicated architectural compositions and grand structures such as Strasbourg Cathedral or St. Paul's as readily as the whorls in a seashell. He was a master at conveying the textural complexity of a lace collar, or the tactile qualities of a feather fan or a fur muff. It is all the more remarkable that he was able to accomplish all this, despite a serious problem with the sight in one eye. Over the course of his lifetime he produced some 2700 separate etchings, and he was still at work as an etcher when he died at age 70.

The delicate lines on an etched plate quickly become worn, due to the extreme pressure exerted by the action of the press. No more than a couple of hundred images can be printed from an etched plate before the overall image becomes indistinct. Printers and publishers therefore frequently had to re-work worn plates so that they could continue in use. The evidence of re-working can be seen in the later states of an image, and there are many examples of this in the collection. In addition to changes made for aesthetic reasons, subsequent states often indicate a change of ownership by adding imprint or attribution information, or altering numeration or dating. This happens because the plates continued in use for many decades, being transferred from publisher to publisher, and being worked on by a variety of people. The plates for The History of St. Paul's first used in Dugdale's edition of 1658, for example, had to be heavily reworked for the second edition, which did not appear until 1716.