This is the first volume of Occasional Papers on the Samuel H. Kress Collection and was published in the memory of Mario Modestini who died on January 28th 2006 in New York. The book marks the tenth anniversary of the advanced training in Old Masters conservation sponsored by the Kress Foundation at the Conservation Center of the institute of Fine Arts of New York University The first part of the book is an overview of historic approaches to the conservation of European paintings and the conservation history of the Kress collection of paintings (which was formed between 1929 and 1961). The second part gives the results of scientific and humanistic research gained in the process of conserving specific Italian and Dutch Old Masters.