Cornstarch Slurry

Introduction

A cornstarch slurry is a simple thickening agent that turns thin sauces, gravies, and pan liquids into silky, glossy coatings in seconds. You mix cornstarch and cold water to create a smooth paste that won’t clump when stirred into hot liquid, making it the fastest way to adjust sauce consistency at the last minute.

Recipe Details

• Prep Time: 2 minutes
• Cook Time: 0 minutes
• Total Time: 2 minutes
• Servings: Makes approximately ¼ cup slurry (enough to thicken 1–1½ cups of liquid)

Ingredients

• 1 tablespoon cornstarch
• 2 tablespoons cold water

Instructions

1. Pour the cornstarch in a cup.
2. Add water and mix thoroughly with a fork. Re-mix as needed to keep the cornstarch in suspension.

Variations

Potato starch slurry: Substitute potato starch for cornstarch in equal measure. This produces a slightly clearer thickened sauce and works well in delicate soups or Asian-style broths.

Arrowroot slurry: Use arrowroot powder instead of cornstarch. Arrowroot thickens at a lower temperature, so add it toward the end of cooking to avoid overcooking the sauce.

Cornstarch and broth: Replace the cold water with cold broth (vegetable, chicken, or beef) to add subtle flavor while thickening. Use the same ratio—2 tablespoons of broth per tablespoon of cornstarch.

Double-strength slurry: If you need a thicker consistency, increase the cornstarch to 1.5 tablespoons while keeping the water at 2 tablespoons. This creates a paste that thickens more aggressively.

Tips for Success

Keep the water cold so the cornstarch doesn’t gelatinize before you add it to the hot liquid. Warm water can cause lumps that won’t dissolve.

Mix thoroughly with a fork immediately before adding to your sauce. Cornstarch settles quickly, so re-stir the slurry if you’ve set it down for more than a minute.

Add the slurry slowly to simmering (not boiling) liquid while whisking constantly to prevent lumps from forming.

Bring the sauce back to a gentle boil after adding the slurry so the starch fully activates and the sauce reaches its final thickness.

Storage and Reheating

A prepared cornstarch slurry will separate within 10–15 minutes as the starch settles to the bottom. For best results, make it fresh just before you need it. If you’ve made extra, stir it vigorously with a fork before using, or discard and prepare a new batch.

Once you’ve added the slurry to a sauce or gravy, the thickened dish stores in the refrigerator in a covered container for up to 4 days. Reheat gently on the stovetop over medium heat, stirring occasionally, as high heat can break down the thickened texture.

FAQ

Can I make a slurry with hot water instead of cold?

No. Hot or warm water causes the cornstarch to gelatinize immediately, forming lumps that won’t dissolve smoothly into your sauce. Always use cold water.

How much slurry do I need for my sauce?

Start with this slurry recipe (1 tablespoon cornstarch to 2 tablespoons water) to thicken about 1 to 1½ cups of thin liquid. For larger quantities, double or triple the slurry proportionally, keeping the ratio the same.

What happens if I add the slurry to boiling liquid?

Boiling liquid can cause the slurry to seize and form lumps. Always add it to gently simmering liquid while whisking constantly, then bring back to a boil to fully cook the starch.

Can I substitute cornstarch slurry with flour and water?

Yes, but the results differ. A flour slurry (using the same proportions) produces a cloudier sauce and requires longer cooking time to eliminate raw flour taste. Cornstarch thickens faster and creates a clearer, glossier finish.