Place covers tightly on jars and shake each jar well, to mix yeast and potato-water thoroughly.

Stand yeast in a warm place near the kitchen range over night.

Jars should be _covered only_ with a napkin.

The sponge should become light and foamy.

In the morning use this freshly-prepared yeast to set sponge for bread.
When preparing to set bread, place in a large bowl 1 pint of potato water, 1 tablespoonful of sugar, 1 pint of the yeast sponge, 1/2 teaspoonful of salt, and use about 3 pounds of sifted flour, well-dried and warmed.