Coffee Experiment: Immersion Cold Brew vs. Japanese Iced Coffee

Cold Brew vs. Japanese Iced Coffee

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Cold brew coffee tastes great and is really easy to make, but there’s just one problem:

It takes a really long time to brew.

Generally, it takes at least 8 hours and many times up to 24 hours, depending on the recipe you’re using.

Fortunately, there are several cold brew coffee methods that are actually quicker than your standard 8 to 24 hour immersion method. Let’s go over these methods real quick.

Slow Drip Cold Brew Method

I’ve heard this referred to as Kyoto style cold brew, but I think calling it “slow drip” is appropriate here because that’s what is effectively happening during the brew process.

You have your water reservoir at the top, which slowly drips into a bed of coffee generally at about 1 drip per second. The brewed coffee then eventually passes down into the final receptacle.

Common slow drip coffee makes look like giant hourglasses or something you might find in a chemistry lab. It’s pretty cool.

Bruer (a kickstarter backed start-up) created a home version of this style of cold brewer a few years ago. It takes about 6 hours in total. You can check out my review of the Bruer here.

Japanese Iced Coffee

I’ve heard many different names for this method as well, including “flash brew”.

While this method isn’t technically cold brew, it’s still the fastest way to make a cold coffee drink at home. The resulting coffee can be very good too if you handle things correctly.

Basically, you brew the coffee with hot water, but the brewed coffee makes instant contact with ice in the carafe or mug.

This method should technically take less than an hour, depending on how fast the ice melts.

There are several coffee makers made specifically for this purpose, but you really don’t need them as long as you have a pour-over dripper like the Chemex or Hario V60.

The Experiment: Japanese Style vs. Classic Immersion

While I’ve compared slow drip to immersion cold brew in the past, I’ve never compared Japanese style iced coffee to any other cold brew method.

The reason I feel it’s important is because of how much faster Japanese style iced coffee is.

Meaning, if Japanese style iced coffee is as good as or better than immersion and/or slow drip, why bother with the extra time you have to invest in those methods?

So today, I’m comparing Japanese Style iced coffee to the classic cold brew immersion method.

The Results

As usual, the sample size was small. But the unequivocally better coffee came from the immersion method, and both Veronica and I were in agreement on this one.

It’s worth noting that because I made a large batch via a Chemex, the results may have certainly been different if I just did a mug’s worth with a Hario V60 (which I may experiment with in the near-future).

How Do You Cold Brew?

Have you tried either of these methods? Have you compared them? Let me know in the comments below!


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  • Hey I was trying to make cold brew coffee at my house. I have tried the immersion process before and I really liked the coffee produced from it. The only problem is the time. The Japanese method sounds cool but I did not like the coffee produced from it. Can you suggest me some other methods to make cold brew which take lesser time and have the same flavor as the one produced from the immersion process.

    • Hey Anuj,

      Your best bet is through the slow drip method. Takes roughly 6 hours and will give you something comparable to immersion method. The Bruer is one of the more popular slow drip coffee makers out there, but there are some others on the market now too.

  • Hi, Benji!

    Immersion cold brew is my favorite coffee! The taste is so rich and flavorful.

    My question is how the time of immersion affect the result? I’ve tried to make 6 hours cold brew Vs. 12 hours cold brew Vs. 24 hours cold brew. And I didn’t get any significant different.

    Have you experimented with time of immersion? What result do you get?

  • I do a 3-day immersion usually. Sometimes I forget and it skips to 4. I’ve found that 12-24 hr produces a concentrate which is certainly palatable at a 1:1 dilution ratio(24 better than 12), but is not appropriate for a 2:1 ratio (too weak). If you let it go for 3 days I’ve found that to be best for a 2:1 ratio. It keeps for at least a week so just have two mason jars going and the time factor isn’t really a struggle. As long as you keep ahead of your consumption who cares if it takes a little longer.

  • Hi Benji!!

    I love my immersion cold brew, but have discovered this recipe and really like it… can’t for the life of me remember where I found it, so my sincere apologies go to the writer.

    *BEST! Japanese Cold Brew*

    You’ll need these: Chemex, Chemex Filter, Grinder, Gram Scale, Timer, Ice Cubes

    Step 1
    Preparation step—make ice cubes with filtered or spring water.

    Grind 48 grams of coffee with a coarse drip grind….21 ish on Encore

    Step 2
    Place the Chemex filter with the tri-fold at the pour spout.

    Step 3
    Rinse the paper filter with hot water.

    Step 4
    Dump the rinse water.

    Step 5
    Carefully remove the wet paper filter.

    Step 6
    Put the Chemex on the gram scale and tare it.

    Step 7
    Add ice cubes until the gram scale reads 290

    Step 8
    Return the rinsed paper filter to the Chemex.

    Step 9
    Put the ground coffee into the filter. Place the Chemex on the gram scale. Tare the scale.

    Step 10
    In a circular motion starting in the center, pour spring or filtered water, just off the boil, onto the ground coffee until the gram scale reaches 48 grams. The goal is to pour gently enough to allow the coffee to bloom and not seep through (for 30 seconds) onto the ice cubes.

    Step 11
    Allow the coffee to bloom for 30 seconds.

    Step 12
    In a circular motion starting in the center, pour water onto the ground coffee until the gram scale reaches about 340 grams. The coffee should take about 2 minutes to seep onto the ice.

    Step 13
    When finished, remove the paper filter, swirl the coffee and enjoy.

    • Awesome, Gail – thanks for sharing! That’s the good ole’ Japanese Style Iced Coffee aka flash brew. Have you noticed big differences when comparing to immersion? I’d imagine a lot less body with this method, especially with those paper filters eh?

  • Hi Benji, this experiment showed that the good old immersion method is the best one, sure it takes a long time but the quality of coffee can’t be compared to the “flash brew” one! Keep up the good work!

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