Thanks. This is really really useful. Clarified some of the confusion I long had.

Kinukcafe wrote:I was experiencing something similar today.

Shot #1
Niche setting: 16
Ratio: 2.5
Brew time: 59s
Taste: 9.0/10

I like the taste of shot #1. It was balanced, good texture and sweet, chocolate with very subtle and nice acidic. But I noticed that the brew time is too long to be ideal (aiming for 30s according to AI rule). So I grind coarser.

Shot #2
Niche setting: 16.5
Ratio: 2.5
Brew time: 38s
Taste: 8.0/10

With coarser setting, I noticed the sweetness is still there but the chocolate is gone. And the acidic and fruitiness (not in the taste note) becomes more prominent. I prefer shot#1 more.

Wonder whether the black this tell me directionally I should stick with 16.0 grind setting, or i should ignore the taste deterioration and keep going coarser to aim for the 30s and hopefully I will be surprising with the quality in cup?

I know I should follow my taste but doesn't 59s sound too far off to be right?

I would follow your taste! Al's "rule" is simply a guideline. In general, if you have a balanced shot at some yield and some time, a lower yield shot will taste similarly balanced with a slightly longer extraction time and a higher yield shot will taste similarly balanced with a slightly lower extraction time. That's all. No hard and fast rules, just general guidelines.

With the Robot, headspace is not really even a thing, so your dose is really whatever you prefer. To Dick's point, grind setting has a large impact on the resulting flavor, especially when you have full control over the pressure and flow, as you do with the Robot. On a more traditional machine, dose and grind size are far more intertwined, as you don't have the ability to preinfuse until you have drops and then ramp the pressure up to whatever pressure you prefer over whatever time you desire. These things really do decouple dose from the equation and allow you to really lean into grind setting and yield as the primary inputs to your approach.

You asked me questions earlier:

Kinukcafe wrote:@jake, when you said you intentionally reduce the dose. How much are you dosing? What difference did you notice after the change? With Al rule, do you still stick with 30a rule regardless of dose?

I had been tending to dose right up to the dispersion screw in my GS/3. This gives me 2-3mm of headspace akin to the "nickel test", which is a great starting point. But I had forgotten that there is a large extraction space that exists with lower doses and finer grinds. My basket will hold 19-20g easily with light roasts and 16-17 with darker roasts. So I typically just adjusted my dose until I could see a light witness mark on top of the puck from my dispersion screen and then stayed there until the coffee was gone. Now, I am comfortable decreasing the dose by 1 or 2 grams from that point and seeing what I find. Generally, those shots are softer, more transparent and bring out more subtle flavors than the higher dose shots with a coarser grind. Bear in mind, I am also experimenting with a fixed brew pressure of 6 bar right now, which is a wild departure from my prior years of experience with a flow control, low flow or low pressure preinfusion and a peak and decline pressure profile from 8 or 9 bar down to 4 to 6 bar over the period of a 30-40 second extraction after 10-20s or preinfusion. So I'm doing things totally different right now. Not because I changed my mind about the benefits of my old approach. but because I'm open to trying new things and the coffee is still quite good. Eventually I'll go back to my old ways (in which dose changes really are not necessary to play with grind setting) and see how I feel about that change once that I'm quite comfortable with my current routine.

Right now, I'd be hard pressed to tell you exactly what it is I might be missing about my old approach with the results I'm getting. Once I go back, I might have a better idea.

Cheers!

- Jake