Following a brief review of the history of age determination of ink, this paper discusses the ink and paper aging process and its measurements, along with some basic requirements. The latter requirements are designed to ensure that the relative age of two inks being compared is not influenced by their composition, the paper they are on, and their storage history. Other topics discussed preliminary to the actual testing are sampling and mass variance, ink aging and paper aging, the shape of the aging curve, and the importance of statistics in age determinations. The remainder of the paper profiles currently known methods for determining and following changes in ink or paper as they age and how these methods are used to establish their approximate age. For inks, the aging process usually begins when they are placed on paper. For paper, it begins after it is manufactured. Most of the methods described in this paper attempt to determine when inks of the same formula were placed on a sheet relative to one another. These determine relative aging. The aim of the methods is not only to determine whether an ink entry was prepared at a later date than purported (detection of backdating fraud), but to answer the more difficult question of whether an ink was placed on a document on the alleged date (detection of date authenticity). 41 references