Building a Leaven

A “leaven” is a combination of flour and water that has been inoculated with a portion of a sourdough starter. In our bakery, building a leaven to mix with was crucial to avoid putting stress on the starter by using and feeding it in mass quantities. A leaven essentially acts as a medium between the bacteria in your starter and your bread dough that allows you to use smaller amounts of starter to achieve the same result. The leaven will be built the night before you intend to mix, and two days or more before you intend to bake, so plan accordingly.

A typical leaven recipe follows: *mix in a glass bowl*

  • 1 part water (room temperature or slightly cooler)
  • 1 part flour (I prefer a half whole wheat/half white flour mix)
  • 1 ounce starter/pound of dough (flexible)

While measuring these parts by weight is the easiest and most accurate method, it can be accomplished using measuring cups. Just be sure use the same vessel for both the flour and the water. For two 2lb. loaves, you would use 4 oz. of starter (1 oz./lb). This is ultimately a rough approximation as every starter behaves differently. It may take some trial and error to find what amount of your starter is enough.

You want to achieve a fairly wet consistency – wetter than you would use for a bread dough. It should be runny enough to pour out of the vessel, if you wanted to, but sticky enough to where it clings to your hand and the side of the bowl. Mix by hand until completely incorporated. Cover with cling-wrap or a lid and leave to ferment between 12-15 hours at room temperature (65-75 degrees).


If you are making a small batch of just one or two loaves and do not want to be bothered by making a leaven, it is perfectly fine to use your starter directly. However, be aware that using your starter will cause your bulk fermentation to speed up. Just be sure to feed your starter approximately 4-5 hours before mixing your dough.