Although quite accurate tests exist for dating of writing supports (paper or vellum), the question of when the ink was applied could not be separately addressed by the same techniques. In a study of the ink edge profile it was noted that a skewed tail extended beyond the dried capillary drawn ink area. The area of this tail seemed to increase with time. Eight paper documents in the period 1200-1972 were examined in ten separate areas by iron spectrum scanning auger microscopy. A regression analysis of the data (area values) versus time showed a correlation coefficient of 0.95. The documents were each of known date from a large private collection. Seven vellum documents were also examined and the correlation was significant at the P = 0.90 level. It proved more difficult to select adequate test areas on vellum owing to surface irregularities such as hair follicles. Some proposals are offered for the correlation between time and area, the sensitivity limits are discussed, and the lack of sensitivity to environmental extremes is described. See also 21-1449 for reference to book. -- AATA