As just about any painter will tell you, the final, decisive act of telling oneself, "This work is finished," may be the most difficult in the entire painting process. It's a decision that has bedevilled every artist from Leonardo to the kindergartener daubing around with his or her first strokes of tempera. It never used to bother me too much when I relied more heavily on single photos than I do now. I'd cover the canvas, go back the next day and touch it up a bit, then, presto, it was done. However more recently, in working on more complex work, usually from multiple photos, and often dealing with conceptual themes, it's got more difficult. As some of you know, I've taken to posting "in progress" work on my Web site asking friends to comment and offer expert guidance. That has helped, although it may also have lengthened the agony in some cases. Touch-ups now often stretch over several days, not just one as before.

Artists down through history have dealt with this problem in a number of interesting ways. Leonardo simply chose to keep the Mona Lisa reportedly working on it over a period of years, postponing the inevitable. Matisse, on the other hand, seems to have enjoyed the "touch-up" period more than any other part. He'd hire a model, cover his canvas, and then spend days, even weeks, without the model perfecting his image (thus saving expensive modelling fees). I seem to recall the story of an artist during the Renaissance who became so fond of a hand and arm he'd painted he chose to paint out everything else, turn the canvas 90-degrees and then begin anew, building a whole new portrait utilising the hand and arm from the first. Other artists, Manet, for instance, were sometimes known to "finish" his paintings by cutting them apart and framing different sections separately. These are extreme solutions of course, but also the stuff which makes life interesting for curators, restoration experts, and art historians.

Harry Cooper and Ron Spronk are into this sort of thing. In particular, they chose to investigate the way Piet Mondrian handled the "when is it finished?" question. Cooper and Spronk work as curators for Harvard University's Busch-Reisinger Museum. The Museum has recently mounted a show entitled, "Mondrian: The Trans-Atlantic Paintings" made up of eleven paintings by Mondrian each having undergone the latest in high-tech detective work studying the apparently excruciating period of indecision Mondrian seems to have gone through in completing these particular works. There is evidence of much scraping away of dried paint, repainting, and repainting the repainting. Using electronic devices employing ultraviolet light, infrared light, x-rays, and digital imaging, they have been able to probe the indecision, and the revaluation process Mondrian seems to have grappled with as he strove to complete these works. Actually there were some 17 paintings in which Mondrian made major changes as much as a year after apparently completing them. The owners of six of the Trans-Atlantic paintings refused to loan them because of the fragility of the paint itself, owing to Mondrian's painted alterations.

In 1940, Mondrian left London and visited New York. There he arranged a one-man show of his work. In returning to London, inspired by the highly charged atmosphere of New York and his American experience, Mondrian decided to revise the 17 paintings he planned to show in New York to be more in line with what eventually evolved into a totally different style - a new era in his work. Until recently, the only evidence of this has been the fact that these works bore two different dates. However, as these paintings have aged, the changes made by the artist have become more and more noticeable, the paintings themselves essentially "giving away" the artist's secret insecurities about his work. Until Cooper and Spronk got their hands on the Mondrians, no one had any idea how they looked before Mondrian touched them up. There were no photos and only sketchy written accounts of the original images.

Ironically, once Mondrian took his newly altered work to New York for the show, the critics were either indifferent, or less than kind. What Mondrian had attempted to do was to bridge the gap between his former simpler style, as seen in works such as Composition with Red, Blue, and Yellow from 1928, and a new, more linear, more complex, New York style as seen later in his famous Broadway Boogie Woogie series. The altered paintings illustrate the folly of such an effort as well as the validity of the old adage many artists, myself included, have all too often ignored - leave well enough alone.