I’m sure many people have had this occurrence say when they have to wipe the steam off and the next day or so they see the streak marks. Sorry if this is a dumb question but as they saying goes “The only stupid questions are those not asked.” But still how does that work exactly? My only theory is that it has something to do with the grease on my fingers but I could be wrong. Thanks for the answers in advance. 
You guessed right.
The oils in your fingers are hydrophobic. But they stick well to glass. So, if steam or frost condenses on the surface of the glass, it’ll accumulate in different concentrations, depending on the distribution of oils, or other contaminates on the surface of the glass making the oils or streaks much more visible.
Reminds me of a mate who, while still living at home but while his parents were away, had a one night stand with a girl he picked up, and the “Adult Cuddles” were held in the parental bed. He (being a complete cad) ushered her out hurriedly when it was all over, only to discover that she had written her phone number in lipstick on the mirror in his parents’ bathroom.
He was very proud he had wiped it all off, until I reminded him that lipstick is full of fats and the like, and the next time one of his parents had a shower, the number would pop up again in the condensation on the mirror.
His parents were terrifyingly formidable, and watching him have shower after shower in a blind panic, testing every cleaning product he could to get even the remnants out of the mirror, made me laugh so hard I think I let out a little bit of wee.
To answer the question, I have heard it said that the surface of glass is macroscopically very smooth but microscopically pitted so that the waxes etc in fingers and lipstick fill the pits in a way that is difficult to remove, and consequently alters the way condensation adheres to the surface.
Whenever I remove someone’s kidneys and leave them in a bath of ice, I use lipstick.
You leave the kidneys in a bath of ice? Weird.
Weirder still, he seems to remove the kidneys with the lipstick.
Reminds me of that Linda Rondstadt song with the line “… put another notch in my lipstick case…”
Damn fierce she was. Feircer than we all knew, apparently.
A man-killer with an appetite for kidneys. Showbiz is full of weirdos.
Every time I stay in a hotel, I write, “I’m watching you” on the bathroom mirror steam.
You are most evil. May I subscribe to your newsletter?
At the very moment I’m killing time in a hotel & will soon take a shower & then start my workday. Thanks to *kayaker *I now have a plan …
Hey, if only once you cause someone to have a The Shining type moment, it is worth it. 
Very sharp, lipstick. I put the kidneys in ice so they don’t spoil.
:smack:
You misspelled Pat Benatar.
is there a standard solution to this, like washing the mirror with alcohol? What should the hotel do to counter such vandalism?
Windex and similar products will do the job.
Who you calling a vandal, bitch?
Well, this oughta get interesting.
Good catch. Those two sorta smoosh together in my head. Haven’t thought about either for years.
Now I am thinking about Pat Benatar, and Linda Rondstat all smooshed together in the shower.
I am still thinking about it.
Tris
I do this too. Or I write “I love you” and a giant heart around it.