How to Thicken a Sauce: Roux, Cornstarch & Arrowroot

The right thickener gives a sauce body without making it heavy or lumpy. Flour-based thickeners suit many gravies and creamy sauces; pure starches are useful when you want a glossier finish. This guide explains roux, beurre manié, instant flour, cornstarch, arrowroot, and an egg-yolk-and-cream liaison.

Sauce too thin? Give its thickener the required cooking time before adding more. For a cornstarch adjustment, mix a smooth slurry with cool liquid, whisk it in gradually, and follow the product’s cooking directions. The comparison below helps you choose a thickener and prevent lumps.

Which sauce thickener should you use?

How starch thickens a sauce

When starch is heated with liquid, its granules absorb moisture and swell—a process called gelatinization. Disperse the starch before it reaches the hot liquid so it does not clump. A roux uses fat to separate flour particles; a slurry mixes starch with cool liquid.

Flour-based thickeners

Flour and roux

Wheat flour makes a sauce opaque rather than clear. All-purpose flour is a practical choice for everyday sauces and gravies. A roux is flour cooked with fat, commonly in equal amounts by weight. Stir it until smooth and cook it to the color required by the recipe before gradually incorporating the liquid.

The flour does not truly dissolve: its starch thickens as the sauce cooks. Whisk thoroughly as you add liquid, then simmer and stir until the sauce is smooth and no longer tastes floury. A darker roux contributes a more pronounced toasted flavor, so choose it for the dish rather than simply cooking every roux until brown.

Beurre manié

Beurre manié means kneaded butter. Work softened butter and flour into a smooth paste, then whisk small pieces into a simmering sauce. Unlike roux, the paste is not cooked beforehand. Allow the sauce to cook after each addition before deciding whether it needs more.

Instant or quick-mixing flour

Quick-mixing wheat flour, such as Wondra, is designed to blend readily into sauces and gravies. Sprinkle it in gradually while stirring and follow the package directions. It is still wheat flour, not a gluten-free starch. Gold Medal describes its uses for sauces, gravies, and light coatings.

Pure starches

Cornstarch

Cornstarch gives a glossy finish and has roughly twice the thickening power of flour, so do not substitute it in equal amounts without adjusting the recipe. First stir it with a little cool water or other cool liquid to make a smooth slurry. Stir the slurry again just before adding it because the starch can settle.

Whisk the slurry into the sauce gradually. For ordinary cornstarch, Argo recommends bringing the mixture to a full boil and stirring for one minute. Then check the consistency before adding more. Follow your product and recipe instructions, especially in mixtures containing substantial acid or sugar. See Argo’s cornstarch guidance.

Arrowroot

Arrowroot is a neutral-tasting starch useful for clear, glossy sauces, including acidic fruit sauces. Mix it with cool liquid before adding it. Add it near the end of cooking and avoid prolonged high heat, which can reduce its thickening effect. Bob’s Red Mill compares arrowroot, cornstarch, and other starches.

Egg-yolk-and-cream liaison

A liaison of egg yolks and cream enriches and gently thickens a sauce without relying on starch. Use the quantities in your recipe. Whisk a little hot liquid into the yolk mixture to warm it gradually, then slowly stir it back into the sauce. This is called tempering. For the wider lesson on how eggs respond to heat, see principles of egg cookery.

Use gentle heat and stir carefully after adding the liaison; boiling can curdle the eggs. Follow the recipe’s final cooking instructions. In broader culinary usage, liaison can also refer to a binding or thickening agent generally.

Fix common sauce problems

• Lumps: disperse flour or starch before adding it, then whisk as you combine the mixtures. If lumps remain, strain the sauce and reassess its texture.
• Too thick: stir in a little of the recipe’s liquid at a time, then taste and adjust seasoning.
• Too thin: allow the chosen thickener to cook as directed before adding another small amount. Avoid adding dry starch straight to a hot sauce.
• Heavy or pasty: use less thickener next time. A sauce should complement the food; it does not always need to be thick.

For a practical next step, learn how to sauté and make a pan sauce, look up terms in the culinary glossary, or browse the recipe directory for dishes to practice.

Compare other ways to build a sauce

Starch thickening is different from keeping oil and water mixed. Read how emulsions work for vinaigrettes and butter sauces, or review au sec and reduction when a recipe calls for concentrating a liquid before the next step.

Try sauce reduction in a free advanced recipe

Our free scallops with cauliflower and lemongrass foam recipe uses reduction and cream to build the sauce, then an immersion blender to create foam. Compare this approach with starch thickening, or explore the Advanced Cooking: Fine Dining class. Nine additional complete recipes require membership.