Ultimate Sauce Thickening Hacks

Wondering how to thicken sauce? If you’re looking at your tomato or Alfredo sauce thinking, “this looks really runny,” don’t fret. It’s not a bust. There are several ways to thicken up your sauces, soups, and gravies so that they cling to your foods, rather than drown them.

You can thicken sauces using pantry staples like flour or cornstarch, or you can do so without adding any ingredients, but instead reducing the liquid. But first, learn this handy hack for testing the thickness of your sauce:

The Spoon Test

How do you know when your sauce is thick enough, besides just eyeballing it? Test the sauce with a spoon. If the sauce coats the back of a spoon you can feel secure the sauce will coat other ingredients. Testing with a spoon is a good way to test the sauce because the temperature of the spoon will cool the sauce a bit, giving an accurate impression of the how thick the sauce will be once it leaves the hot pan and cools to the temperature it will ultimately be served at.

How to Thicken Sauce by Reducing Liquid

Reducing sauce on the stove is an excellent way to thicken sauce naturally without adding any thickening agents, like cornstarch or flour. This method works particularly well for tomato-based sauces, because added starches don’t always play nicely with the acid in tomatoes.

In addition to thickening a sauce, reducing concentrates the flavors when water that would otherwise dilute the intense flavors deepens while the reduction occurs.

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  1. Pour the ingredients for your sauce into a pot. Turn the heat to medium-high and stir the ingredients.
  2. As the sauce heats, it will begin to boil. Notice the sauce is thickening as it heats. As the bubbles become larger in the pot, watch the sauce closely. Do not let the bubbles become too large or they will creep up the side of the pan and boil over. When the bubbles begin to enlarge, reduce the heat to low to allow your sauce continue to cook further (deepening and strengthening its flavor), or serve the sauce immediately.
  3. Your sauce has completed cooking when it has reached your desired thickness (consistency) and taste. Keep in mind sauces, especially in the cases of reduced sauces made with sugar and gelatin, will continue to thicken as they cool.
  4. Test the sauce with a spoon.

How to Thicken Sauce With Flour

So long as you’re not gluten-free, flour is an excellent option that you’ll likely always have on hand. Not only can you use it to thicken sauces, but it makes an excellent thickener for gravies and soups as well. When added to liquid, the starches in the flour expand, helping to thicken whatever you add it to. There are two ways to thicken with flour: Either make a roux or a slurry.

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Use Flour to Make a Roux

A roux is a classic thickening agent consisting of equal parts fat and flour by weight. In most cases, people choose to use butter. Here’s how:

  1. Heat butter over medium heat. When a sprinkle of flour causes it to bubble, you’re ready to add the rest of your flour.
  2. Add remainder of the flour and whisk until your mixture forms a thick paste and is golden brown in color.
  3. Add roux to your sauce and whisk to combine.
  4. Test the sauce with a spoon.

Use Flour and Water

Combine 2 tablespoons flour with every 1/4 cup cold water and whisk until smooth. Add the mixture to your sauce over medium heat, and continue to stir and cook until you’ve reached your desired consistency. Test with a spoon.

How to Thicken Sauce With Cornstarch

Cornstarch is an excellent gluten-free alternative to flour, and it won’t make your sauce look cloudy. A general rule of thumb is for every cup of liquid in the recipe, use 1 tablespoon cornstarch.


  1. Combine equal parts cornstarch and cold water. Stir together until smooth.
  2. Pour into your sauce and cook over medium heat, stirring continually, until the sauce reaches your desired consistency.
  3. Test the sauce with a spoon.


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