At that time, the mechanisms underlying the action of yeasts and other leavenings were not understood, and reliable commercial products were not available. Bakers obtained yeasts from brewers or distillers or made their own by exposing mixtures of flour and water to the open air. If lucky, they could capture useful wild yeast and keep some alive, regularly feeding it for ongoing use and trying to avoid contamination. Women who made their own ale could use the brewing dregs or "emptins" in their baking.