Ilsted was one of the few Danish artists to have worked in mezzotint and the only member of the "Copenhagen Interior School" who loved and collected prints.

He began creating prints as a student at the Academy in 1882. By 1909, he had abandoned etching and devoted his time exclusively to mezzotint. Ilsted's warm regard for Dutch genre painting of the 17th century influenced his art as much as his appreciation of the orderly, deserted interiors painted by his celebrated brother-in-law, Vilhelm Hammershoi (1864-1916). Ilsted also learned from Whistler about the rich nuances of greys and he often released both black and white versions of an image from the same plate.

His prints are imbued with a sublime light which he creates through his grounding methods, the use of chine colle', and selective wiping techniques during the inking process.