A Barista’s Guide to Cold Brew: Perfecting Your Grind Size and Brew Time

I believe cold brew is the absolute best type of iced coffee to make at home. Why? Because the brewing process is incredibly forgiving, allowing you to make a delicious batch even without professional equipment. Recently, friends have been asking me about the specifics of grind size and steeping time, so today I want to walk you through how to master these variables to create your perfect cold brew.

The Foundation: Getting the Ratio Right

While the questions were about grind and time, we can't ignore the coffee-to-water ratio, as all these parameters are connected. I recommend a starting powder-to-water ratio between 1:12 and 1:13. In my experiments, I’ve found that a ratio higher than 1:13 (e.g., 1:14) can make the coffee taste a bit thin and flat. On the other hand, a ratio lower than 1:12 (e.g., 1:11) can result in a brew that is overly concentrated and difficult to drink.

How to Choose Your Grind Size and Brew Time

Cold brew is essentially a low-temperature immersion brew. This means the temperature is a constant (cold!), leaving us with two main variables to control the final taste: grind size and time. Whether you want your coffee to be bright and crisp or rich and full-bodied, it all comes down to how you balance these two factors.

Finding the Right Grind Size

It’s easy to understand that the finer you grind your coffee, the faster its flavor will be extracted. However, I need to point out a common pitfall: coffee that is ground too fine is not suitable for cold brew. The tiny particles tend to clump together into a dense mass, which prevents the water from properly extracting the coffee’s flavor.

After many tests, I've found that a grind size similar to what you would use for a pour-over works beautifully. If you're using sieves, that’s a grind where 70-85% of the particles pass through a #20 screen.

Perfecting Your Brew Time

Time is more straightforward: the longer you steep the coffee, the more flavor compounds are extracted, and the stronger the brew becomes. But more isn't always better. My tests show that steeping for more than 24 hours can introduce unpleasant nutty or woody bitter flavors. Conversely, steeping for less than 8 hours will likely result in a weak, watery coffee that lacks substance.

The ideal steeping window for cold brew is between 8 and 24 hours.

You might wonder why there is such a massive 16-hour range. With espresso, a single second can drastically change the taste, and with a pour-over, a 20-second difference is noticeable. This is because those methods use high heat (and pressure, for espresso) to extract flavor efficiently. Cold brew, on the other hand, uses water between 4-10°C and is completely static, with no outside force like pressure or agitation. Extraction is therefore extremely slow and gentle, giving you a very wide, forgiving window.

You can use time to target specific flavor profiles:

• 8 Hours: The coffee will have a bright acidity and a refreshing, crisp body.

• 16 Hours: The flavor will be more rounded and full-bodied, with a perfect balance of sweetness and acidity.

• 24 Hours: The coffee will be at its richest and most intense, with a thick mouthfeel and balanced profile.

My Go-To Cold Brew Recipe

Here is my personal, time-tested method for making fantastic cold brew.

First, I always prefer to use light to medium-roasted coffee beans. You’ll need a clean, sealable container.

1. Measure out 40 grams of coffee. Grind it on the finer side of the recommended range (about an 85% pass rate on a #20 sieve).

2. Pour the grounds into your container, then add 480 milliliters of cold water.

3. Use a wooden stick or spoon to stir gently, ensuring all the grounds are wet, then seal the container.

4. Place it in the refrigerator to steep for 12 hours.

5. After 12 hours, take it out and filter the coffee to remove all the grounds.

The coffee is ready to drink right away, but for the best flavor and mouthfeel, I recommend putting the filtered coffee back into the fridge to chill for another 4 hours before serving.