The little hairline crack that saved my morning routine

I have this mug I got 8 years ago at a gas station outside of Flagstaff. It's a plain white diner mug with a blue rim. About a year ago I noticed a hairline crack running from the rim down about an inch. Most people would toss it. But here's the thing. That crack lets me know when my coffee is cool enough to drink. When the mug gets to the right temperature the crack darkens just a little from the steam. I've timed it against a thermometer about 10 times now. It's always within 2 degrees of 140 Fahrenheit. Has anyone else ever had a damaged mug that actually got more useful?

2 comments

2 Comments

anna_green4817d agoMost Upvoted

Saw a guy on Reddit who drilled a hole in his mug to test the same thing.

sean_perry17d ago

Huh, that's actually a different thing. The Reddit guy drilled a hole to let steam escape and prevent boiling over. Your crack is more like a built-in thermometer, way more useful than a simple vent hole.