He started writing artist biographies, with one on Gerard David appearing in 1895, another about Hans Memling in 1901, and a final and most ambitious one on the Van Eyck brothers in 1908, with a revised edition in 1912. Meanwhile, in 1902, he organised the ambitious Exposition des primitifs flamands à Bruges, the largest exposition of works by Early Netherlandish painters up till then, which was groundbreaking and the source of many publications and research.