Many people, when they first stand in front of a fresco, think that they're looking at a work straight from the hand of the artist. While there is some truth to that though, what many don't realize is that there are many other hands that have worked, manipulated, and restored the painting over the years. The next time you're standing in front of a fresco, admire the genius of the artist, but also think about the many ways that the painting has survived throughout the years.
Visitors exclaim over the beauty of Michelangelo's Sistine Chapel paintings and imagine him on the scaffolding painting every inch of the ceiling. But he's not the only one. In fact, just over a decade ago, well-intended conservators were standing there, brushes in hand, cleaning and recreating what was believed to be Michelangelo's original intent. Not everyone agreed with the restoration, which, over the span of 15 years, cleaned off the years of dirt and smoke damage to "restore" the paintings to their vibrant past.
There was considerable debate whether or not it was over-cleaned from a misinterpretation of Michelangelo's original working method. Regardless of how true it was to the original (and it's hard to tell at this point in time,) Michelangelo's work has been altered by those who intended to save it. The work is not just a Michelangelo anymore, but has become its own entity, a product of everyone who has touched it.
I hadn't seen first hand the degradation of wall painting until I visited the Rocca, a 14th century castle in Spoleto, Italy. There, I saw frescoes chipped away, destroyed or marred with graffiti from years ago. The damage, too, has a history. The Rocca was once a palace and in another age a prison and the walls tell its story.
Here the works were less mediated by restorers and more by everyday life. I may not have seen the pristine view, but reading old-fashioned graffiti was just as interesting to me as the artist's intent.
Conservation is where the world of art, history, and science combine. Using modern day technology and historical evidence to help infer what was there before, works of art are preserved to the best of our knowledge. The question of how to do so has plagued critics since Michelangelo's time and good intentions have often hurt more than they have helped. The bottom line, what you see in front of you isn't just the hand of Michelangelo or an unknown artist from time past, you're viewing a cultural artifact that has grown and changed with time. The hand of the artist mitigated through the eyes (and hands) of those who have cared for it. The next time you're faced with a fresco you shouldn't just think "wow, that artist was great," you should also think "so that's how it survived."
Cather, Sharon, ed. The Conservation of Wall Paintings: Proceedings of a Symposium Organized by the Courtauld Institute of Art and The Getty Conservation Institute., 1991. Available online (pdf)