Put flour into a crock and gradually mix water into flour until smooth and the consistency of pancake batter.
Cover with a cloth.
Keep in warm place 48 hours.
Mixture will bubble.
When brown liquid comes to top and bubbling stops, it is done.
Skim off foam.
Fill crock with cold water; stir.
Flour settles to bottom in a few hours.
Pour off clear liquid and refrigerate in jars.