Traditional bread making relies on starters made of flour, water and wild yeast gathered from the air. Though the bread making process takes longer than it would with store-bought yeast, bread made with a starter achieves tastes and textures hard to come by otherwise. Some people add store-bought yeast, sugar or other ingredients to starters, but none of these is necessary for a successful starter.
Pour flour and warm water into your clean container. Stir until blended.
Cover your container with a loosely fitted lid, a damp cloth or any cover that allows circulation. Place covered container in a warm spot where it will not be disturbed. A room temperature of 70 to 80 degrees F is ideal.
Remove and discard ½ of the mixture from your container every 12 to 24 hours. Mix in ½ cup flour and ½ cup warm water. This is called "feeding" your starter, and you should do it every day for at least the first week.
Check before each feeding to see if your starter is active, meaning yeast and bacteria cultures are thriving. An active starter will be puffy and bubbly, it will double in size between feedings and it will smell yeasty like beer. Do not use a new starter to make bread until after at least seven days of consecutive feedings.
Store your active, lightly covered starter in the refrigerator or somewhere warmer like your counter after at least seven consecutive days of feedings. If you refrigerate it, you only need to feed it once a week. If you store it outside the refrigerator, you need to continue feeding it once or twice every day.
If water gathers on top of your starter, you can stir it in or pour it off; it won't do harm. Remember to reserve some starter when you bake bread to feed and store for next time. If your tap water is heavily chlorinated, use spring water or drinking water when making your starter. If you need to feed your starter on a day when you are not baking bread, give the discarded part of your starter to a friend or throw it away. A well maintained starter could live for over a century; some have!
Do not store your starter in a tightly closed container; pressure will build and your container can burst. If your starter turns gray or pink, or if it looks moldy, discard and start over. Thoroughly clean your container at least once a month to avoid mold, storing your starter in a comparable container while you clean. Do not use metal storage containers. They can be reactive, ruining your starter.