During the first decade of the 20th century a startling phenomenon was witnessed in exhibitions of oil paintings throughout France: “at retrospective exhibitions of art, many modern pictures which on their first appearance were greatly admired for their brilliance and freshness, seemed so darkened and tarnished as to be hardly recognizable.” The reason for this phenomenon is linked by the author to the practice of oiling out and the application of retouch varnish. In his first part article of a five part series, James Robinson, exposes this faulty practice and shows how it developed as a remediation of sinking in from the 18th century to the present.