If you have visited the Sistine Chapel or plan to visit, it might be worth visiting your local library to read the lovely, detailed article in the April 2019 "Wall Street Journal Magazine" re: the on-going conservation efforts/process re: The Sistine Chapel
When we visited (two different times) on trips to Rome, I remember guides telling us the humidity is kept at very specific levels, but I learned sooooo much more reading this article, and the photos are also lovely.
One sample tidbit: For removing non-soluble contaminants, it involves taking undyed delicate Japanese Bib Tengujo Paper, 19 x 30 inches, flattening it to the wall, then moistened with distilled water and a goat-hair brush, left in place for 3 minutes, then slowly peeled away...repeated, if necessary.
There is also interesting info about the technology that is in place to monitor and control all sorts of situations in various weather conditions.
The article also mentioned 25,000 visitors a day sometimes. WOW!
Both my husband and I found the article totally fascinating, and we are not professional preservationists or scholars, but truly do appreciate historic beauty. We both sort of geeked out on this article :)
Before someone asks for me to attach a link, links (usually) will not give access for non-subscribers. But, you could Google the article "Divine Intervention" by Cullen Murphy, and you might get lucky to gain access. Worth the trek to a library, if you are interested.