Piet Mondrian, "Trafalgar Square," 1939-43. Oil on canvas, 57" x 47."
In terms of Mondrian's late paintings, the vibrant, syncopated "Broadway Boogie Woogie" tends to dominate the the conversation, and rightly so - it would have been exceedingly interesting to see what he would have come up with if he had been able to continue on that track for a few more years (he died of pneumonia in 1944 at age 71).
But while "Broadway Boogie Woogie" represented a significant departure from the typical Mondrian pictorial vocabulary, "Trafalgar Square," finished around the same time, was also a big move, even though it bears a stronger resemblance to the earlier works.
In terms of size, the main body of Mondrian's output would be classified as easel paintings or "cabinet pictures" - the middle scale so common to Impressionism and Cubism, made with the domestic setting in mind. Both "Broadway Boogie Woogie" and "Trafalgar Square" (along with the unfinished "Victory Boogie Woogie") represented a shift to a larger scale. It would be tidy to say that the Dutchman's move to NYC influenced him to work larger, but Trafalgar Square was started in London (hence the title). Still, it's easy to believe that New York's skyscrapers, so aesthetically linked to his earlier works, convinced him that bigger scale was the correct move. The fact that "Broadway Boogie Woogie," painted entirely in New York, is in a similar scale to "Trafalgar Square" tends to support this view.
The shift in scale is somewhat difficult to appreciate when looking at "Trafalgar Square" in reproduction, because the stripes are scaled up in proportion to the canvas - the part to whole relationship is similar to the smaller paintings of the '20's and '30's. But in person, it makes for a very different picture.
The scale is in keeping with a three-quarter-length portrait, and as such the picture demands a different sort of attention - it is more like meeting a person than peering into a small window or diorama or fish tank. The picture is still spatial to be sure, but the larger size encourages the viewer to look at the picture as opposed to into the picture. The scale also demands that it be hung relatively high, so it is impossible to apprehend it completely at eye level - you have to look up to see the top, which adds to its more commanding presence.
More importantly, the new width of stripe allows it to do double-duty, as it were; it can function as line (as it typically did in Mondrian's work) or it can function as plane. This latter distinction is quite important, because when the lines are perceived as planes, it's a short trip to seeing them as an unbroken ground behind the white and primary squares - especially when the panes of white and color get small at the sides and bottom of the picture. The five white and two yellow rectangles at the bottom left look dangerously close to dislodging themselves from the grid, and this subtle breakdown in the stability of the space reverberates throughout the rest of the picture, even the areas at the top where the the lines tend to function more like masonry, as they did with the earlier work. The ability to get that much variety from such a Spartan vocabulary is awesome.
Had Mondrian lived just a little longer, would he have been influenced to an even greater scale by his new neighbors and admirers in New York: Newman, Pollock, Kline, Rothko, et al? I think that stripe would have looked pretty good at about a foot wide.