How To Make A Cornstarch Slurry (Ratio & Easy Step-by-Step)

Looking for an easy way to thicken soups, gravies, and sauces? Learning How To Make A Cornstarch Slurry requires just 2 simple ingredients and 60 seconds of whisking for lump-free, silky smooth thickening!

What Is a Cornstarch Slurry?

A cornstarch slurry is a simple mixture of cornstarch and cold water used as a thickening agent for sauces, soups, gravies, stews, and more. It’s the go-to thickener in Asian cuisine and is prized for creating smooth, glossy sauces without altering flavor. Best of all, it’s naturally gluten-free, dairy-free, and vegan.

Unlike flour-based thickeners (like a roux), a cornstarch slurry doesn’t require cooking with fat and works almost instantly when added to hot liquids. This makes it the fastest and easiest way to thicken any dish.

Ingredients & Substitutions

You only need two ingredients:

• Cornstarch — the thickening agent
• Cold water — must be cold to prevent clumping

The standard ratio is 1 part cornstarch to 1 part cold water. For example, 2 tablespoons of cornstarch mixed with 2 tablespoons of cold water.

Substitutions and Variations

• Vegetable broth instead of water for richer flavor (keep it cold)
• Arrowroot powder — works similarly, slightly more neutral finish
• Tapioca starch — gives a slightly chewier, more elastic texture
• Potato starch — another gluten-free alternative with similar thickening power

How to Make a Cornstarch Slurry (Step-by-Step)

1. Measure your ingredients: Use a 1:1 ratio. For every tablespoon of cornstarch, use one tablespoon of cold water.
2. Whisk thoroughly: Combine the cornstarch and cold water in a small bowl. Whisk or stir with a fork until completely smooth and lump-free.
3. Add to your hot dish: Pour the slurry slowly into your simmering sauce, soup, or stew while stirring continuously.
4. Cook briefly: Continue cooking for 1-2 minutes until the mixture thickens to your desired consistency. If it’s too thick, add a splash of liquid to thin it out.

Tips & Tricks for the Perfect Slurry

• Always use cold liquid: Mixing cornstarch with cold water prevents clumping. Adding it directly to hot liquid creates lumps.
• Mix right before using: Cornstarch settles quickly, so whisk the slurry just before adding it to your dish.
• Add gradually: Pour the slurry in slowly while stirring constantly. You can always add more, but you can’t take it out.
• Don’t overcook: Cornstarch can break down if cooked too long, leading to a thinner or spongy texture. Add it toward the end of cooking.
• Start small: Begin with 1 tablespoon of slurry per cup of liquid and adjust from there.

What to Use a Cornstarch Slurry For

Cornstarch slurry is incredibly versatile. Here are the most common uses:

• Stir-fries and Asian sauces: The classic use — creates that signature glossy coating on vegetables and protein.
• Gravies and pan sauces: Thickens drippings or broth into a smooth gravy in minutes.
• Soups and stews: Adds body to thin soups without changing the flavor.
• Pie fillings and sweet sauces: Perfect for thickening fruit fillings and dessert sauces.
• Vegan cream sauces: Create rich, creamy textures in dairy-free sauces.

Cornstarch vs Flour: Which Thickener Should You Use?

Both cornstarch and flour are popular thickeners, but they work differently:

Pro tip: If substituting, use 1 tablespoon of cornstarch for every 2 tablespoons of flour. Cornstarch has roughly twice the thickening power.

Is Corn Flour the Same as Cornstarch?

No! Cornstarch is a fine white powder made from the starchy part of the corn kernel — it’s a pure thickening agent. Corn flour is made by grinding the entire corn kernel into a yellow powder and is used for baking (cornbread, tortillas). They are not interchangeable.

Gluten-Free Thickening

Cornstarch is naturally gluten-free, making it an excellent choice for those with celiac disease or gluten sensitivities. Other gluten-free thickener alternatives include arrowroot powder, tapioca starch, and potato starch.

The Science Behind Cornstarch Slurry

Cornstarch thickens through a process called starch gelatinization. When the starch granules are heated in liquid, they absorb water and swell dramatically, thickening the surrounding liquid. This is why cornstarch must be added to hot liquids to activate — but mixed with cold water first to prevent clumping.

One important note: overcooking can cause the starch molecules to break down, thinning your sauce. That’s why it’s best to add the slurry toward the end of cooking and only cook for 1-2 minutes after adding.

Helpful Tools

• Whisk or fork: Helps mix cornstarch and water thoroughly for a lump-free slurry.
• Measuring spoons: Ensures the correct 1:1 ratio every time.
• Small bowl or measuring cup: Makes it easy to mix and pour the slurry into your recipe.

Cornstarch Slurry

Commonly used in Asian cuisine, cornstarch slurry thickens dishes and sauces to the perfect consistency.

5 from 2 votes

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Prep Time 1 minute min

Cook Time 0 minutes mins

Total Time 1 minute min

Course Sauce, Vegan Basics

Cuisine American, Asian

Servings 1

Ingredients

  

1x2x3x

• ▢ 1 part cornstarch
• ▢ 1 part cold water

Instructions

 

• Mix the cornstarch and water together thoroughly right before adding into a sauce, gravy, stew, soup or anything else you’d like to thicken.
• If you are using 1 tbsp of cornstarch use 1 tbsp of cold water.

Video

Notes

Cornstarch slurry needs to be added when the dish or sauce is already heated as cornstarch requires heat in order to activate its thickening properties. It can be used to thicken soups, stews, sauces, gravies, and much more. 

Note: Nutritional information is approximate values and can vary significantly depending on the specific brands of ingredients used. Disclaimer: This information is for general guidance only and should not be considered professional nutritional advice.

Nutrition

Serving: 2tbsp | Calories: 30kcal | Carbohydrates: 5g | Protein: 1g | Fat: 2g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 1g | Cholesterol: 2mg | Sodium: 60mg | Potassium: 30mg | Fiber: 1g | Sugar: 2g | Vitamin A: 30IU | Vitamin C: 2mg | Calcium: 6mg

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