Giorgio Vasari relates that copperplate engraving, closely dependent on the technique of niello, was invented around the 1460s by a Florentine goldsmith, Maso Finiguerra (1426-1464), who experimented with the first prints from copper plates engraved by burin. Although this information is undoubtedly exaggerated, it is no less valuable for its account of Finiguerra’s habit of obtaining from his niello work sulphur moulds and prints on paper, using a complex procedure that was actually close to the technique of copperplate.

What is copperplate printing? Copperplate is a technique for printing from incisions into metal matrices, which could be done directly (burin, and also niello, mezzotint, drypoint) or using acids (etching, aquatint, soft-ground). This technique is called ‘incision’ because the printing ink runs into the grooves made by the burin or the acid.

In burin engraving, the image is scored into the metal plate with a fine scalpel with a steel point (burin). The plate is then inked over and cleaned, so the ink remains only in the incised parts. Finally, the print is obtained through the pressure of a special press onto previously dampened sheets.

For etchings, the metal plate is covered with a thin layer of wax or varnish. Then, this protective material is removed, leaving the parts to be printed uncovered. The next step is to immerge the plate in aqua fortis, a solution of water and nitric acid or ferric chloride, more suitable for copper, which corrodes the parts left uncovered (mordant). The plate – once removed from the acid, dried and all residual wax or varnish removed – can be inked and put through the press.