When A Smudge Isn’t What You Think It Is

I've worked at many museums around the world as a certified art restorer assistant. The real experienced professionals restore old paintings to their original beauty by repairing damage. I am, on the other hand, tasked with cleaning the dirt that builds up on paintings after decades or centuries.
I like doing detailed, careful cleaning and seeing painting transform back into like-new conditions. When I first started working, I preferred cleaning monochrome paintings as it was easier working with just black, white, and gray colors. As I got better at my job, I started to enjoy working with abstract paintings and the simple beauty of Impressionist landscapes. Though, I never learned to like portraits and still find them boring.
Not too long again, I was sent to the National Gallery and the Munch Museum in Norway to clean their Edvard Munch paintings. Munch made four versions of his iconic painting known as The Scream. Three of them are in these two museums. I had finished two of the paintings and, by then, I had really gained a very intimate knowledge of Munch's style and his unique brushwork. So I definitely noticed the small, but unmistakable, smudge next to the shoulder of the screaming man as I finished cleaning the last painting. It hadn't been on any of the other two paintings. I checked my cleaning supplies to see if I had somehow accidently mixed in some white paint. But, no, everything was normal. I don't even have white paint, only cleaning supplies. So what happened? I was in a panic.
I couldn't sleep that night. The next morning, I went to see the art museum director. As I told him what happened, he looked at me without saying a word. Then he put his hand on my shoulder and laughed. He said, “Oh, don't worry at all! That smudge has been there for more than 100 years, and no one knew what it was – until yesterday. And now you'll be one of the first people to know.”
He told me that art experts always thought the smudge was from bird droppings, because Munch often worked outside. But yesterday the University of Antwerp finished a very detailed study using a special X-ray and other techniques. It turns out that the white mark actually came from candle wax! Boy was I relieved. And the whole art world was excited to have solved this mystery.