Well right from the get-go we can see that you are ignorant of how the three [normal] states of matter behave, solid, liquid and gas.
(Not dealing with plasma here.)
You see,
Sauron did not "evaporate". Matter evaporates when it goes from a solid to a liquid, and then from a liquid to a gas; or if it is in liquid form already and then changes to a gas. You put an ice cube in a pan and heat it on the stove; first it changes to a liquid and then it boils away (evaporates) as a gas.
Some types of matter, dry ice (frozen CO
2 ) for example, change from a solid to a gas without passing through a liquid stage. This is called
sublimation.
Sauron went directly from a solid eye ball to a gaseous eyeball; that is, he
sublimated, not evaporated.
Tolkien understood 6th grade science.
Gandalf understood 6th grade science.
Elrond,
Galadriel,
Celeborn,
Cirdan all understood 6th grade science.
Tom Bombadil understood it but didn't care if someone evaporated, sublimated, or disintegrated.
You, however, obviously do not understand 6th grade science. Please don't post any more questions on Quora until you have taken a 6th grade science class.