The artistic approach of Caspari relied on clear lines and a focus on the individual. He produced many works in the silhouette style, such as his Silhouet van een man, naar rechts. These pieces required a precise hand to define a profile without the use of colour or internal detail. In his more traditional portraits, such as those of Paulus van der Ven or Jeanne Jacqueline Drognat-Landré, he maintained a sense of directness. He avoided the heavy ornamentation of earlier eras.

Modern collectors find value in the graphic quality of these portraits. The monochrome nature of his silhouettes fits well with contemporary interior design. His depictions of Dutch citizens like Bernardus Verwey provide a factual record of a specific social class. These prints offer a sense of history without the visual clutter of more decorative styles. They remain relevant for those who appreciate the clarity of the neoclassical period.