Cleaning the Artwork

I went to the Museum of Modern Art today to see the exhibit "Inventing Abstraction" before it closed.  On my way up to the 6th floor, I went by this window looking out on the courtyard.  I was so surprised to see a stepladder next to one of the sculptures, and apparently one of the curators, carefully cleaning this piece of art.  She was working very carefully, cleaning small areas at a time. I could have done it much quicker with a garden hose, soap and a long-handled brush, but that is NOT how you clean a valuable work of art!