He would align the paper over a genuine banknote, place the two on a piece of glass, and trace the resulting image.

[3][7] He used a camel’s hair brush to put colors on the note, imitated the silk threads with red and blue inks, and suggested rather than duplicated the intricate geometric lathework.

[3][7] Notably, he omitted the line crediting the Bureau of Engraving and Printing from all of his bills,[3][7] and some of them were also missing the counterfeiting warning.

He was apprehended by the United States Secret Service in March 1896 when he paid a bartender with a $50 banknote, the note got wet, and the ink began to smudge.

[7] Ninger was somewhat romanticized during his time, as almost a "Robin Hood"-like character, whose crimes were deemed "victimless", both because only the extremely wealthy could afford the bills that he was forging, and also because with the proper art connections, one could stand to profit by receiving a Ninger work.