So I really like beans and cook them a lot, pintos are likely my favorite. When I made some last night it reminded me that even with almost identical cooking methods sometimes beans will cook into a pretty starchy liquid that is almost like a 'bean sauce' This is my favorite end result. Last night I was cooking them and it seemed like it wasn't gonna happen so I let them cook down a bit, but the 'sauce' remained watery.
My first guess is starch, and I'm pretty sure that's right, but why would it differ from batch to batch? How much starch is leeched during the soaking process?