Putting the flexibility of Tetsu 4-6 to the test

One of the reasons that led me to choose the Tetsu 4-6 recipe when brewing our daily morning V60 was the supposed flexibility of the technique. Kasuya-san designed it as a two-phase process where the first 40% of water is split into two pours, and the remaining 60% split into a further one to three pours.

Phase One controls the flavour of the final brew, where the ratio between the first two pours determines the balance of sweetness vs acidity (a.k.a. brightness). Phase Two controls the body of the coffee, which increases as the number of pours is increased.

Philocoffea, Kasuya-san’s coffee company, explains this in more detail in one of their blog posts.

I don’t follow the Tetsu 4-6 recipe exactly though, and have tweaked it slightly. For example, I use a 1:16 coffee-to-water ratio instead of the recommended 1:15.

Why? Because my coffee dosage is 25gm and a 1:16 ratio results in 400gm of water, a nice and friendly round number which makes me happy, unlike the relatively unfriendly-looking 375gm. Yes, numbers have personalities too.

Details of my modified recipe are given below:

  • 25gm medium ground coffee (3-6-0 on my 1Zpresso JX-Pro)
  • 400gm water for a coffee-to-water ratio of 1:16
  • 94°C water temperature
  • Bloom (i.e. first pour) 3x coffee weight (i.e. 75gm) in 45secs
  • Remainder of 40% (i.e. 85gm) in 45secs
  • Pour 3 pulses of 80gm each, starting at 1:30, 2:15 and 2:45
  • No stirring, no swirling, no nothing
  • Resulting bed will be relatively flat, but not totally flat
  • Full drawdown around 3’30”

After repeating this daily for several months, I was finally comfortable enough to start tweaking things, to experience first-hand how it would affect the taste of our brew.

To help me remember easier, I used different multiples of my coffee dosage when tweaking Phase One i.e. in addition to my current 3x (75gm) bloom, I also tried 2x (50gm) and 4x (100gm).

For Phase Two, in addition to my current three additional pours (i.e. total of five pours), I also tried two (i.e. total four) and one (i.e. total three) additional pours. All these would be done with grind size (1Zpresso JX-Pro 3-6-0) and water temperature (94°C) held constant.

There are quite a few moving parts, so I modified the useful graphic in Philocoffea’s blog post to create the customised summary chart below to match my specific brewing parameters. So basically, my current recipe corresponds to “Standard x Strong”.

Although Philocoffea provided specific pour timings when doing a total of five pours, they didn’t do the same for the four and three pour variants, but I think it’s reasonable to assume the same start times. So, for four pours (“Medium”), I started Pour Three at 1:30 and Pour Four at 2:15. Similarly, for three pours (“Light”), I started Pour Three at 1:30.

For total brew time, they provided a guidance of 3:30 for five pours, but again, they didn’t do so for the other variants. Using the same grind size, my empirical observation was that total brew times for Medium and Light were 3:15 and 3:00 respectively.

Now that I had the mechanics sorted out, it was time to choose my test subject. I had just opened a bag of Nylon Coffee’s Columbia Altamira, one of the best beans we’ve tried so far, and decided to use it as our guinea pig.

Standard x Strong

My default recipe yielded a full-bodied cup with dominant Ribena notes and a long and pleasant aftertaste. The tasting notes on the bag indicated “currants, red grapes and chocolate”, and while currants were prominent there was no hint of chocolate.

Sweet x Strong

Reducing bloom amount was supposed to increase the sweetness of the brew, but while it resulted in stronger body I couldn’t taste additional sweetness. The Ribena taste did become less prominent while some chocolate notes started surfacing. In a head-to-head comparison, “Standard x Strong” > “Sweet x Strong”.

Bright x Strong

Increasing bloom amount did increase acidity, exactly as advertised. The resultant cup had a lighter body but had good balance, with an overall flavour that was closest to the stated tasting notes. Between the three choices for Phase One, this was clearly the best. It went really well with the old-school apricot cake that we got from Prince Coffee House.

Bright x Medium

Keeping to “Bright” for Phase One, I reduced the number of Phase Two pours from three (“Strong”) to two (“Medium”) and got a terrible siap-siap tasting cup. But I couldn’t blame it on the recipe change because we had bananas for breakfast, which always make our coffee taste super astringent. Trying again the next morning, we got a cup with a good balance of flavours but having a lighter body than “Bright x Strong”, consistent with the expected result.

Bright x Light

Reducing the number of pours down to the minimum had the most drastic effect so far. The cup was definitely very light tasting, almost approaching tea-like. All hints of chocolate were gone and there was almost no aftertaste. Of all the combinations we tried, this was our least favourite.

I could have continued with the exercise and tested the remaining four combinations but the beans were quickly running out, so we stuck with our favourite choice of “Bright x Strong” and enjoyed what was left in the precious bag.

So, does Tetsu 4-6 provide the flexibility that it was designed to do? My small sample test seems to indicate that it mostly does.

Reducing the total number of pours definitely made the final cup lighter and changing the amount of water for the bloom clearly changed its flavour, but I didn’t manage to taste the increased sweetness with a smaller bloom.

I might try again with another bag of beans and maybe something more fruity like an Ethiopian Guji would yield different results.

If you use the Tetsu 4-6 to brew your V60 filter coffee, and my observations have piqued your curiosity, why not try this fun little exercise yourself and see if you get similar findings?

Note: Featured image inspired by, and adapted from, Philocoffea.

2 thoughts on “Putting the flexibility of Tetsu 4-6 to the test

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