Probably unsolvable on the basis of the data available:
I’m trying to make my recipe for homemade ricotta cheese (irrelevant spoiler: I used too much vinegar so it tasted vinegary) and step one, I’m heating some milk in a pan on my electric stove. After 30 seconds, I notice that there seems to be some milk on the heating element, so I take the saucepan off, wipe the milk up, and start again. Same thing.
After three repetitions, I decide there must be a minute hold in the saucepan (??) so I pour the milk into a different saucepan and try again. Success. Well, vinegary success.
But I experiment with the first saucepan to see if I can find the problem. I pour some cranberry juice into that saucepan and set it down on a sheet of paper towel on the counter.
Nothing. No cranberry juice on the paper towel after a half-hour.
Do I throw the saucepan out because of the milk or keep it because of the cranberry juice?
Maybe the pan only leaks when it’s hot. A crack or pin hole could expand enough to leak when the pan is heated but not when it’s cold. Is this an aluminum pan?
What’s your recipe for ricotta? I use 6 cups whole milk, 2 cups heavy cream and 3 TBSP white vinegar. It never tastes vinegary. I’m actually making some today.
Is the handle hollow at all? I wonder if you could have spilt milk on the handle when you first filled the pan, and it dribbled back out of some cavity or crevice there, but not all at once.
It’s super unlikely the stainless pan (almost all have multiple plies) sprung a pinhole that’s otherwise invisible. Other possibilities depend on, basically, your milk handling.