The importance of underpainting

Since I like painting in a structured, organized manner, it was necessary for to me spend time studying the techniques of the Old Masters, rather than say, the techniques of 20th century modern masters, who I also admire. Over the years I experimented with all four of the historical approaches to realistic oil painting. But it was in the techniques of the 16th and 17th century Italian and Dutch master painters that I found comfort, relief and possibilities. After many years of study I realized that the main difference between 16th and 17th century Italian and Dutch and modern painting techniques is directly related to the magic mediums they used, whatever they were, AND how they broke down their working procedure into a series of distinct passages executed in a predefined order.