Adapted from: "Vegetable Soups from Deborah Madison's Kitchen". "Barley is a thirsty, thirsty grain. It can drink up to around four times its volume in water--or the soup liquid--so I strongly suggest a two-hour soak before cooking so that you end up with soup rather than a barley dish. Of course you can always thin a thickened soup with water, but flavor is lost when you do that. If you don't have time for a soak, at least cover your barley with hot water while you prep everything to give it a a head start."