Hi! I have two containers of flour one of which is self-rising. The labels have gotten mixed up. Is there a way to tell which flour is the self-rising? Best,

--Mike

Your question got me to thinking about all sorts of different ways to tell the difference, but after a little head scratching,  I think this is maybe the easiest.

Take two tablespoons of flour from one of the containers and mix it with about three tablespoons of plain vinegar.  The consistency should be about that of pancake batter or heavy cream. If necessary, add more liquid. Make another similar mixture with flour from the second container.  Leave them sit for a couple of minutes.

Self-rising flour is regular flour with baking powder and salt already added to it.  Baking powder is a combination of baking soda and a powdered acid (see Baking Soda vs. Baking Powder). The surface of the mixture made with self-rising flour will have small bubbles over it from the reaction of the vinegar with the baking soda.

The mixture made with regular flour may have a few bubbles from air that got mixed in, but far fewer than the other one.

The same thing will happen if you just use plain water, but the vinegar makes it easier to see the difference.