Starters contain acid that can react with metal, so only prepare sourdough starters in nonmetallic bowls. Be sure to use a large bowl since the starter will significantly increase in volume and may overflow a small bowl.If you don’t use the starter immediately, stir it and transfer it to a clean glass, ceramic or plastic container. Cover loosely and store in the refrigerator. Always bring the starter to room temperature before using. This will take 2 to 12 hours. The longer it stands at room temperature, the more tangy it will be.To use, stir the starter and remove the desired amount. Bring to room temperature if refrigerated, and use in the recipe as directed. Replenish the starter with equal amounts of flour and water to restore the volume; stir. (For example, if 1/2 cup starter was removed for a recipe, combine 1/2 cup all-purpose flour and 1/2 cup warm water. Stir into starter.) Let the replenished starter stand in a warm place (80° to 90°) for 12 to 24 hours or until light and bubbly. Stir starter; cover loosely and refrigerate.If you don’t use any starter with in 2 weeks, you will need to nourish it to keep it active. To nourish, remove half of the starter and share with a friend or discard. Transfer remaining starter to a large nonmetallic bowl. Add equal parts of all-purpose flour and warm water. Let stand in a warm place (80° to 90°) for 12 to 24 hours or until light and bubbly. Stir starter and transfer to a clean storage container; cover loosely and refrigerate.If used and replenished or nourished at least once every 2 weeks, the starter should remain active indefinitely.Discard a starter if it develops an offensive odor, changes color or becomes slimy or stringy, which means it’s spoiled. Sterilize the storage container before using it for a new batch of starter.