Reduction

• Reduction produces a syrupy consistency while it gives you complete control over viscosity. But although reduction is natural and reliable, it works for some sauces better than others because as the water evaporates -- which is how reduction produces a syrupy sauce -- flavor, color and aroma intensify. The sauce must contain a carbohydrate or gelatin to thicken. When you reduce a gelatin-based sauce to a syrup, it's called a glace; when you reduce a sugar-based sauce to a syrup, it's called a glaze. Glace means "glaze" in French, but it primarily refers to meat glazes such as glace de viande, or veal glaze. To create a syrupy sauce through reduction, hold off on seasoning until the finish, if you can. Heat the sauce to a gentle simmer in a heavy-bottomed pan and cook until it reaches the desired consistency or reduces in volume by one-half to three-quarters. Season to taste.

Arrowroot

• Arrowroot is as close to a pure starch thickener as you'll find. Unlike cornstarch, arrowroot can handle food acids, but not dairy products. Arrowroot imparts a lustrous finish that suits dessert sauces better than gravies and meat sauces. To produce a syrupy consistency in a dairy-free sauce, mix 1 tablespoon of arrowroot with 1 tablespoon of cold water for each 1/2 cup of sauce and then whisk it in. Arrowroot thickens instantly, and you don't have to cook the starchy taste out.

Cornstarch

• Although arrowroot and cornstarch perform the same function in a sauce, they aren't interchangeable. Cornstarch doesn't respond well to food acids, which negates its thickening power. But cornstarch works well with dairy where arrowroot comes up short. To thicken a non-acidic sauce, mix 1 tablespoon of cornstarch with cold water for every 1/2 cup of sauce. Whisk it into the sauce and then bring the sauce to a simmer, cook for about 3 to 5 minutes, and serve.

Sugar

• Sugar and heat create a naturally thick, versatile syrup that's used in everything from cocktails and candy making to conserving fruits. The only thing about adding sugar to create a syrupy sauce is, obviously, it makes it sweet, which limits its applications in savory cooking. However, many sauces -- particularly Asian sauces and the French gastrique -- make sweetness balanced with acid the cornerstone of the flavor profile. To thicken a dessert sauce with sugar, dissolve 2 parts sugar to 1 part water on the stove over medium heat and whisk it. Heat the dessert sauce over medium and add the heavy syrup 1 tablespoon at a time until it reaches the desired consistency. To thicken a savory sauce with sugar, make a gastrique by reducing an acid -- wine or lemon juice -- until thick and almost dry. Add the sauce base, such as stock, along with half as much sugar. Adjust the taste as needed with acid and salt, and reduce until it reaches the desired consistency.