Some baker of sourdough and a few other types of bread have what they call “starter dough”. this dough contains yeast from which they make all their bread. some starter dough is more than 100 years old. the dough has to be “fed” more flour and water on a regular basis for it to remain usable. why must the starter dough be “fed”?

Fresh sourdough starter is a wonderful resource. Bread, pancakes, waffles, cake… there are so many delicious directions you can take with sourdough. The key: maintaining your sourdough starter so that it’s healthy, happy, and ready to go when you are almost there! Once you’ve successfully created your starter, you’ll need to feed it regularly. If you bake a lot of sourdough treats, you may want to keep it on your counter, at room temperature. While this means feeding it twice a day, it also means your starter will be ready to bake with at the drop of a hat! However, many of us don’t want the commitment of twice-a-day feedings. If you’re a more casual sourdough baker, it’s possible to store your starter in the refrigerator, feeding it just once a week.

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."