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In a number of modern variants such as microfabrication etching and photochemical milling it is a crucial technique in much modern technology, including circuit boards.
In traditional pure etching, a metal (usually copper, zinc or steel) plate is covered with a waxy ground which is resistant to acid.
Apart from his prints, there are two proven examples of his work on armour: a shield from 1536 now in the Real Armeria of Madrid and a sword in the Germanisches Nationalmuseum of Nuremberg.
An Augsburg horse armour in the German Historical Museum, Berlin, dating to between 15, is decorated with motifs from Hopfer's etchings and woodcuts, but this is no evidence that Hopfer himself worked on it, as his decorative prints were largely produced as patterns for other craftsmen in various media.
Etching has often been combined with other intaglio techniques such as engraving (e.g., Rembrandt) or aquatint (e.g., Francisco Goya).
The switch to copper plates was probably made in Italy, and thereafter etching soon came to challenge engraving as the most popular medium for artists in printmaking.
Its great advantage was that, unlike engraving where the difficult technique for using the burin requires special skill in metalworking, the basic technique for creating the image on the plate in etching is relatively easy to learn for an artist trained in drawing.
One of his followers, the Parisian Abraham Bosse, spread Callot's innovations all over Europe with the first published manual of etching, which was translated into Italian, Dutch, German and English. However, from 1880–1950 a photo-mechanical ("line-block") variant was the dominant form of commercial printing for images.
The 17th century was the great age of etching, with Rembrandt, Giovanni Benedetto Castiglione and many other masters. A similar process to etching, but printed as a relief print, so it is the "white" background areas which are exposed to the acid, and the areas to print "black" which are covered with ground. He used the technique to print texts and images together, writing the text and drawing lines with an acid-resistant medium.