For the graphic execution of the portrait, Haid made use of a technique, known as mezzotint from the mid 17th century. While in copperplate engraving, the dark areas and lines are created by engraving the plate, the mezzotint process is exactly the opposite: The scraper tool is used to remove the light areas from the deep black base of the copper plate. Because this allowed particularly soft and gentle image components such as hair and robes to be expressed realistically, the mezzotint technique was primarily used for the reproduction of portraits. However, it was also used for natural history illustrations, such as the moon globe project of the then head of the Göttingen observatory Tobias Mayer (1723-1762).
