Just want to add to what Fear Itself is saying. Dry beans added to water do not result in increased volume after soaking. The water travels into the dry beans resulting in an increase in the bean’s volume, and a decrease in the volume of water in the pot. Net result is the same. My evidence is doing this last weekend when I soaked white beans.
Michael Ruhlman suggests do not soak, for best flavor, and salt halfway through cooking for fewer broken beans. Distilled water produces the best result, with alkaline water producing mushy beans and too-hard water leading to beans that don’t soften properly.
Side question: Lentils are labelled as not needing a pre-soak so as to avoid gas production. Have people found this to be the case?
In regards to the salt issue, it turns out that soaking beans in salt water actually improves the consistency and makes them creamier. So much for the old cooking myth that it toughens them. One cite.
I’ve also never had any problem with the quick-soak methods myself.
Wasn’t sure on that one, so thanks.
Measured out 240ml of beans and water last night, 240ml this morning.
I have soaked many a pot of beans and while the results vary with the type of bean and some other factors, I have frequently ended up with a significantly larger final volume than the net volume of water and dry beans. This is one of those cases where it’s not a simple matter of adding the two volumes; the beans change consistency and at some level expand further than by just the amount of absorbed water. At a guess, they develop added space between granules, starch chains or perhaps even molecules. The beans also grow larger and develop larger spaces between them, so while the compressed volume might be the same, the measured volume can be considerably more. (I’d further guess the effect is more noticeable with larger beans; small white beans and such might not move apart as much.)
Inexperienced cooks and die-hard physical chemists are welcome to cut it close; I’ve learned better, the hard way. (And to the latter, I point out that 100mL of water and 100mL of alcohol equals 200mL of solution… right?)
And what constitutes that added space, if not water?
It’s quite common advice (the no-salt, that is). I mean, you even see Ruhlman repeating not salting beans until they’re half-cooked. I don’t blindly trust Cooks Illustrated (and I often disagree with them), but they seem to be right about this, at least in my attempts at doing beans.
Air and other gases, I would assume.
It shouldn’t be hard to visualize the point: a dried bean is almost as solid as plastic or glass. A cooked bean has a much looser, grainy texture. The space between the granules is neither bean nor water, but it makes up pot volume. The space between beans also increases as they get larger - again, it’s neither bean nor water, but it’s part of the net volume.
Please note that I’m speaking from 30 years of cooking experience, with a scientific bent. This is not a theoretical lab experiment, but reality as I’ve established it in many, many real-world trials. You’re welcome to insist that the volume can’t exceed water+beans, but I’m not going to come over and clean up your stovetop for you.
Well my totally non-scientific results are in and the decision is-
Delicious. Soaking didn’t entirely kill the gassy effects, but it did see to lessen them. In any case, the beans and ham were wonderful.
If that were true, the beans would float.
I stand by my assertion. Any kind of beans, submerged in water, will increase in volume at the same rate the water decreases in volume, with no net change in the water level.
This applies only to the soaking phase, so don’t start with anecdotes about your pot of beans that boiled over. Not relevant.
FI, you’re free to logic your way along as much as you like on the topic. I’m especially fond of debates where the pure-science crowd keeps stomping its foot and shouting, “But that’s impossible!”
I am talking about the soaking phase, although the problem continues into the cooking phase. And I have considerable experimental data that indicates the overall expansion often greatly exceeds the volume of beans plus the volume of water.
I suggest that, lab-style, you are looking at the calculated expansion of each bean and disregarding the net size of the resulting pile. It may well be that, bean by bean, the excess expansion is minimal. But if you take a box of golf balls and magically transmute them into tennis balls, your box will need to be significantly larger than the increased spherical space alone.
I’m so tempted to run out and buy a bunch of dried beans and find the camera…
…but that would mean I’d have to cook them, and that would mean I’d have to eat them, and I haven’t gotten over my poverty induced aversion to beans yet.
(Although, ironically, we’re having chili tonight…with canned beans.)
I re-read his polling of various people, and to be fair, he cites Russ Parsons (food writer) as salting at the start, Steve Sando (owner of Rancho Gordon heirloom beans) halfway through for fewer broken beans, with Sando then clarifying that he salts “when the beans are my bitch” (when it starts smelling like beans rather than mirepoix and water, or maybe 3/4 done).
Oh, and he notes that few Mexican cooks/chefs soak their beans.
First off…I didn’t know the type of water would give different out comes. Need more specifics.
I want to make chile…but the beans wont bean properly. Want something between Tender but not mush. 
Second…
If you fill a pot with beans to the brim…and fill the rest with water to the brim…I’m inclined to say the beans will spill over, after saturation of the water. Just like rice.
But, in a specific volume, like in an unheated pressure cooker filled to the brim with beans and then water to the brim, then close the lid for 24 hours. The beans will have no choice but to expand within the limits of the container.
It wont explode either…because the mass inserted was equal to the confined area in the initial filling…Probably consisting of a pot shaped block of beans you can make pie out of later…for the Inlaws.
One cup of beans(pinto)only leave room for just under 2 ounces of water. Certainly not enough to hydrate the beans enough to expand.
Yeah, I found out that salt added during cooking to certain proteins…maybe just vegetable proteins?..will toughen them and it will take longer to cook. Explained why it always took so long to cook my beans, as I always used to add salt. Not anymore! 
This is all that matters 