A poolish is a sponge starter has the consistency of a thick liquid and is very easy to prepare. It requires only a few hours of fermentation before it can be used, but it produces some excellent qualities, such as depth of flavor and a pleasing aroma usually in found breads prepared with the more time consuming sourdough method. The recipe for a poolish starter will differ depending on the type of bread being prepared, but often the only difference is in the quantities of the ingredients that are used in the starter in relation to the quantities of the ingredients in the full recipe. This does not apply to the yeast, which does not change proportionally as the quantities of the other ingredients are changed.
A biga starter is an Italian version of the sponge leavening method or French poolish. It differs from a poolish in that it is firm and dough-like instead of batter-like and it requires a longer fermentation period. Breads made with a biga starter feature a subtle flavor, a porous texture, moist, open crumb, and a champagne aroma. Like other starters, there are several methods for preparing a biga starter, but the biga recipe will differ with each type of bread being made. Often the same recipe for the biga sponge starter can be used for a number of breads if the quantities of the ingredients in the biga starter are changed proportionally to the quantities of the ingredients in the full recipe; however, the quantity of yeast usually does not change proportionally.