Roux - Flour and Fat

A roux is a cooked mixture of about 50 percent sifted bread or all purpose flour (used because of the higher gluten) and clarified fat, usually butter

There are three basic types of roux, each contain the same basic ingredients but differ in coloration which is a result of the cooking process.  The darker the roux the longer it has been cooked 

White roux used for béchamel sauce, velouté (basic white sauce) and some soups
    White roux, made with butter
    Blond roux, made with butter
    Brown roux, used to thicken brown sauces
    Dark roux is used in the preparation of sauces from the Southern United States especially the    Louisiana Kitchen.  Because of the high heat and cooking time required this roux is made with oil instead of butter

Every roux should be cooked until the taste and acidity of the raw flour is no longer evident.

The amount of roux needed to thicken a soup is about 12 ounces to a gallon and to thicken a sauce about 12 to 15 ounces per gallon.

A rule that must be headed is to never mix a stock and roux together at the same temperature as this will result in lumping or poor quality,  All roux sauces must be simmered after the roux is added