Last week I spent some time explaining why Robert Irwin was so particular about the way his objects looked, why they had to be just so—why he was dubbed one of the “finish fetish” artists.

And now, for an abrupt change, I want to talk about a big, fat flaw smack in the middle of his exhibition at the Museum of Contemporary Art San Diego through April 13.

It’s in the show’s largest installation, in a piece called Who’s Afraid of Red, Yellow and Blue. (More about other parts of the show here and here.)

^{Photos by Philipp Scholz Rittermann}

The piece, whose title references a Barnett Newman painting of the same name, was first installed, in 2007, in a spacious New York gallery. But the old refurbished train depot that would be its home in San Diego was even bigger.

So Irwin added to it.

First, the basic structure: All the panels are made of lightweight aircraft aluminum and painted with dozens of layers of super-shiny acrylic so that they end up looking like pools, not paintings. With like colors hung above and below one another, and with the succession of the three colors influencing each other in their reflections as you walk past and see them from different angles, the piece is a playground of perception. At certain points, because of the depth of the reflections bouncing off each other from top to bottom and back again, people in the gallery appear to be two stories below the surface of the floor panels, or two stories above the panels that are suspended from the ceiling. (You can’t make it out in this image, but this image gives you an idea.)

But the funny part, the part you can completely miss, is that Irwin allowed a mistake into his work: In adding two panels to each color in order to make the installation larger for San Diego, he let in two panels of a slightly darker blue than the other four blue panels. You don’t notice it at first. But once you do, you can’t stop. It’s a major gaffe for an artist as exacting as Irwin, but it’s sort of endearing, too, an admission of ease late in his career.

A guard in the gallery on the day I visited said an art historian who came to the exhibition asked about the darker color, then refused to believe it had been a mistake, knowing that Irwin plans everything.

The guard couldn’t convince the art historian, and they ended up in a deadlock. But the guard told me he was there when Irwin was overseeing the installation in the gallery, and he saw Irwin’s realization and response. The artist smiled, he said, and shrugged.

Does the flaw detract from the piece? Yeah, it sort of does. It compromises the uniformity of the blue pool—is this area deeper because it is darker?—and it takes away from the finessed perfection of the piece. It also is harder to see the reflection in darker panels. At the same time, it makes me smile and shrug, too. Finessed perfection has its limits.

Coming up: Why the bad lighting on one of Irwin’s paintings is perfect, and what’s up with Irwin in Seattle right now.