Hello! Lots of sources say that using salted butter to grease a pan can lead to sticking, but I don't see any information on why this occurs. I'm new to baking and just trying to learn, so any insight is appreciated. Thank you!
That's a myth. There is nothing about salt that would make a cake stick. In fact table salt has a melting point of over 1400°F, so it cannot even melt during baking.
Butter makes a poor pan grease because of the milk solids and natural sugar. The water in butter will begin to evaporate at 212°F. Around 266°F the milk solids will begin to brown. The solids are sticky. Doesn’t matter if it's salted or unsalted butter.
Below is a photo of some butter I recently browned. About 10% - 20% of milk solids stick to the bottom of the pan. Even after scraping the pan with a spatula, milk solid residue remains as it is sticky when cooked. It is best to use a BAKING (not cooking) spray, then line the bottom of the pan with parchment baking paper.
Baking grease made with equal parts vegetable oil, flour, and shortening works very well. But butter as a grease always poses a risk of sticking, even when the buttered pan is dusted with flour.