This question popped up in my mind when I was going through the explanations of coffee ring effect. Almost all of the explanations state that “the outer rim of the drop evaporates faster”, but unfortunately I couldn’t find any explanation WHY it dries faster than the inner part. Is it something to do with height? area? surface tension being stronger/weaker on the edge? temperature?
Sorry for not adding any image, but what I actually meant was this:
[uneven evaporation of drop](https://www.ds.mpg.de/3208834/original-1559025408.jpg?t=eyJ3aWR0aCI6ODAwLCJoZWlnaHQiOjYwMCwib2JqX2lkIjozMjA4ODM0fQ==–01a65b684acafba312604a11b22490739a711d36)
As you can see from the image, the arrows indicating the magnitude of evaporation are stronger on the edges in 2D cross section. I was wondering why it is stronger there, rather than being even on crest and on the flanks of the drop