What causes butter to "hiss" in the frying pan until I shake it? When frying an egg, I drop about a tablespoon of room temperature butter in the frying pan and turn it on medium flame. As it's melting, it starts to make a hissing sound, and bubbles a bit. Then, I take the pan and give it a shake, spreading the butter around the pan - and the hissing stops, even after putting the pan back on the heat. What's going on?
The hissing and bubbles are due to the butter's water content turning into vapor. It stops when there's no more water and only fat/milk solids remain on the pan. When you shake the pan you help release the last few water/vapor droplets into the atmosphere, thus speeding the process.