Who was Van Gogh writing when he wrote : " It is a kind of painting that rather changes in character , and takes on a richness the longer you look at it . " ?
Unlike the character studies Van Gogh wrote to his brother Theo in November 1882 that he had drawn a portrait of Jozef Blok ( F993 ) , a street bookseller who was sometimes called " Binnenhof 's outdoor librarian " .