The white stage is reached once the flour loses its raw smell, after about 5 minutes of cooking and stirring. Although slightly grainy in texture, it is much smoother than it was at the beginning. The mixture is bubbling vigorously and the color is a little paler than when the clarified butter and flour were first combined.
The blond stage is reached after about 20 minutes of continuous cooking and stirring. The bubbles are beginning to slow, and the aroma has taken on nuances of popcorn or toasted bread. The roux is now tan colored, very smooth, and thinner than it was at the white stage.
The brown stage is reached after approximately 35 minutes of cooking and stirring. It be a peanut butter-brown color and its aroma is more pronounced and sharper than the nutty nuances of blond roux. The roux is now thinner, and the bubbling has slowed even more.
The dark brown stage is reached after about 45 minutes of cooking and stirring. It is the color of melted milk chocolate. Its aroma will also mellow from the strong, roasted flavor of brown roux and will actually smell a little like chocolate. The roux is no longer bubbling, and is very thin.