The mezzotint method, often called the black manner, allows for soft tonal transitions without the use of cross-hatching or dots. Siegen used a small toothed wheel called a roulette to roughen the copper plate. This created a surface that held ink to produce deep, velvety blacks. His portraits, such as the Portret van keizer Ferdinand III and Portret van Elisabeth Stuart, show how this technique captures subtle light on skin and fabric.

Collectors today value Siegen for the atmospheric quality of his work. His prints provide a sense of depth and mood that differs from the sharp lines of traditional etchings. The high contrast between dark backgrounds and soft highlights makes these pieces suitable for contemporary interiors. Works like the Portrait of a Man or his depictions of royalty offer a sophisticated aesthetic for those who appreciate historical printmaking techniques.