In a glass or ceramic bowl or jar that has been scalded, combine flour and yeast, add water and blend well. Cover with plastic wrap and pierce with fork to release gases. Place in a warm, draft-free location at an even 85F for 18-24 hrs; stir several times daily. Refrigerate until ready to use. If you have several starters, keep whole wheat separate from others to preserve its own distinctive flavor. Whole wheat starter does not have as much rising action as that made with white flour; you may have to plan longer rising times. To replenish, always use whole wheat flour.