According to an account by one of Whistler's biographers, the American printmaker Joseph Pennell, quoted by MacDonald, "Whistler once told us that he worked about three weeks on each of the Thames plates. He therefore must have spent on dated plates alone thirty-six weeks in 1861, leaving but fourteen weeks for other work and for play . . . it was about the Black Lion Wharf, one of the fullest of detail, that we especially asked Whistler . . . there is no doubt that the Thames plates, notably the Black Lion Wharf, have, for artistic rendering of inartistic subjects, and for perfect biting, never been approached by anybody."
