Sauce thickening
The secret behind what thickens sauce perfectly in just one step.
We’ve all had it happen: the sauce is on the simmer, and the flavors are wonderful, but it’s just too runny. You’re looking for richness, silky smoothness, and spoon-coateness — not thinness. That’s where the knowledge of sauce thickening enters the scene. Whether you’re concocting an earthy gravy, tomato sauce, or finishing off a stew, the proper recipe can totally transform the result.
Slurrying is one of the simplest and most reliable methods to thicken sauce — one that many professional chefs use religiously, but few home cooks apply to best effect. Here’s what makes the technique work, how to use it, and how to prevent the off-flavours that normally accompany using traditional thickeners.
What Is a Slurry and Why Does It Work
Slurry is an uncomplicated mixture of cold water and starch, typically cornstarch but sometimes arrowroot, potato starch, or tapioca starch. The difference between a roux (a mixture of equal weights of fat and flour that is cooked beforehand) and a slurry is that the slurry is introduced after you are already cooking your sauce.
The reason it is effective is that the starch granules swell and absorb when heated with liquid. By adding a slurry to simmering sauce, the starch thickens the liquid fast without affecting the colour or taste.
This is especially useful for:
- Stir-fries
- Soups
- Pan sauces
- Gravies
- Any dish where you want that smooth, glossy consistency without heavy flour or cream
It’s gluten-free by default and adds no raw flour taste — perfect for clean flavour and fast results.
Ingredients and Ratio — Getting the Slurry Right
The basic rule for a cornstarch slurry is simple:
1 tablespoon cornstarch + 1 tablespoon cold water = thickens about 1 cup of liquid.
Key tips:
- Always use cold water — adding starch to hot liquid will cause clumps.
- Mix the slurry well until smooth, with no lumps.
- Use small amounts at first. You can always add more if needed.
If you are using arrowroot or other starch, reduce the amount slightly since these tend to thicken faster than cornstarch. And when using wheat flour, you should be cooking it for a little longer to prevent that raw taste.
Slurry is great when you want a neutral flavour. It won’t alter your tomato sauces, broths, or glazes the way a roux or butter-based thickener might.
Step-by-Step: How to Add a Slurry to Your Sauce
Here’s how to use the thickening agents like the slurry method without messing up your dish:
- Mix your slurry: Combine equal parts cornstarch and cold water in a small bowl. Stir until fully dissolved.
- Bring your sauce to a boil: This is critical. A slurry only activates once the sauce reaches boiling temperature. Medium heat may not be enough.
- Add the slurry gradually: While the sauce is at a full simmer or gentle boil, slowly pour in the slurry while whisking.
- Watch the change in consistency: The sauce will begin to thicken almost immediately. Keep stirring for 30–60 seconds.
- Stop when you reach the desired consistency: You don’t have to use all the slurry. Add it in small amounts and observe. Once your sauce coats the back of a spoon, you’re done.
Pro tip: If you over-thicken, just stir in a splash of broth or water to loosen it back up.
Real Kitchen Example: Thickening Buffalo Chicken Sauce
In one of my favorite videos, I made a buffalo-style sauce using a food processor and used the slurry method to finish it. The sauce was bubbling in a hot pan, and the flavor was spot on — but it needed more body to cling to the chicken.
Here’s how I did it:
- I prepped my slurry in advance — 1 tablespoon cornstarch + 1 tablespoon cold water.
- Once the sauce was at a strong simmer, I slowly poured the slurry into the center while stirring.
- Almost instantly, the consistency changed. It went from runny to velvety and glossy.
The key was going slow, watching how it thickened, and stopping right when it felt right. That’s the secret sauce (pun intended) to great consistency.
Common Mistakes to Avoid When Using a Slurry
Although one of the simplest sauce thickening agent methods is the slurry method, there are various common errors that can stop it from functioning as it should. Here are the most common errors and how to rectify or avoid them altogether.
1. Adding slurry to cold or lukewarm sauce
One of the biggest misunderstandings is trying to thicken a sauce that hasn’t reached the right temperature. A slurry only activates when it’s introduced to a hot liquid — ideally at a gentle boil. If your sauce is only warm, the starches won’t swell properly, and you’ll end up with a thin, underwhelming texture. Always wait until your sauce reaches a full simmer or boil before stirring in the slurry.
2. Using hot water to make the slurry
When you combine cornstarch (or starch) with hot water, it gels instantaneously — and produces lumps before you are able to pour it into the sauce. This ruins the whole endeavor of creating a slurry. The fix? Use cold or room temperature water to create a smooth pourable consistency.
3. Adding the entire slurry at once
It is quite easy to end up with an overly thick or chunky sauce by adding the whole amount at once. It is safer to add it gradually, stirring and observing how the sauce is behaving. You might find that you never actually use the whole amount.
4. Over-thickening the sauce
If you add too much starch, the sauce ends up being sticky and gluey or too gelatinous — unpalatable. Use the rule of thumb for how to thicken sauces is adding 1 tablespoon cornstarch to 1 cup of fluid. Don’t feel compelled to add extra unless you are doubling the amount to cook a huge amount.
5. Forgetting to stir while adding
You’ll want to stir the sauce as you pour in the slurry. If the mixture sits still, the starch can coalesce in one area and cook unevenly, resulting in lumps or rubbery areas. A whisk is the best tool for good incorporation.
6. Expecting results without boiling
Some home cooks expect the sauce to thicken immediately upon adding the slurry, even if it’s below a simmer. That leads to the assumption that the slurry “didn’t work.” Remember, starch thickening happens only at the boiling point. Be patient and keep cooking at medium heat or higher until you see the change.
7. Not adjusting the seasoning after thickening
The thickening also has the effect of slightly dulling flavors. Check the consistency once you’ve reached the desired consistency and sample the sauce. You might find you need to add salt, vinegar, or spice to rebalance the flavor.
By avoiding these most frequent errors, your own sauces are going to be smoother, silkier, and taste better — just the sort you find at the best restaurant. Slurry does not become active unless the fluid is at the boil. Add it too soon and it does nothing.
Final Thoughts
When it comes to sauce thickening, the slurry method is hands-down one of the most practical, reliable, and approachable tools any home cook can have. It’s fast, requires minimal ingredients, and gives professional results with very little effort.
Whether you’re finishing a pan sauce, building a gravy, or rescuing a thin soup, slurry is your secret weapon. Just remember: cold water, small amounts, and a boiling sauce — and you’ll have full control over the flavour, consistency, and finish of your dish.
Ready to upgrade your recipes? Try the slurry technique tonight — and say goodbye to bland, watery sauces for good—and try adding egg yolks for richness.