Other
Biddington's: Engravings vs. Etchings
An explanation of the differences between engraving and etching techniques. There are sample works of etchings by Sigmund Abeles and Bill Murphy.
Other
Warnock Fine Arts: Printmaking
Article that explains and gives examples of many printmaking processes. Includes details about relief printing, lithography, serigraphy, intaglio and more. Links to books and artist's examples.