Coffee with a splash of physics: how to make the most out of your brew (opens in new tab)

In the pour-over section, the authors hit on a good point about height and creating a vortex in the slurry. Water temperature and flow rate are important variables too. Combined with the coffee grounds' quality (i.e. grind consistency) and whether it has fines or lots of chaff will also dictate how long it takes to draw down and therefore whether the pour height's effects will change if static.

I do like the advice grind coarser and extract with more water -- that's made my V60 coffee quality fairly consistent, but everyone's mileage will vary based on how they like their coffee and the roast profile.

There are so many other variables that didn't get a mention: Coffee varietal

Water hardness (and even which other ions are present in the water) and its effects on acids and other compounds that highlight certain varietal's defining characteristics.

Vessel temperatures.

The filters used (materials, paper thinness).

Pouring patterns (circular, concentric, hypotrochoid, more?)

The filter shape and material.

Even the grinder used conical vs. flat burrs and high RPMs vs. low RPMs creates palpable flavor profile differences.

The rabbit hole goes deep and continues to expand.

And here I am microwaving a cup of yesterday's brew of drip coffee that sat on the burner for two hours.

There is another solution: Get a machine with flow control and a pressure gauge on the group head. You can saturate the puck at low pressure to avoid dry pockets, then ramp the flow rate up until the group head pressure peaks. If the pressure starts to drop you can increase the flow to maintain the group head pressure.

As for the 6 bar course grind theory: You may maximize the extraction of soluble coffee mass, but the concentration will be lower. It does not take very much extra water to ruin the taste and texture of a latte.

> The bottom line of the team’s experiments and mathematical modelling is that to get the most reproducible shots just use less coffee and grind it more coarsely.

This seems to go against conventional wisdom, which says that less coffee will reduce brewing time and a coarser grind will also reduce brewing time, and consensus seems to be that you want a brewing time somewhere between 20 and 30 seconds. Or did I misunderstand something?

Anyway, the reasoning seems sound, so I'm going to have to give this a try.

For an entire book about the topic, see "The physics of filter coffee" by Jonathan Gagné.

Also

> This can be achieved using an espresso machine (figure 1), or with smaller contraptions at much lower pressures such as a moka pot or AeroPress.

Please, just stop. They're not even remotely close.

I roast coffee professionally, and there's just a few things that will make up 98% of your coffee quality, and none of them have to do with technique. And without these no level of technique will ever compensate.

1) Sourcing high quality coffee to the roast level you enjoy. Try a lot of different coffees - from "Ultra Light" to "American Light" to "Medium" to "Dark" - and find what you enjoy, then find a roaster that produces those coffees to a high quality standard. There will not be a ton of these roasters in your country. Maybe even just a couple, even if you live in the US.

2) A good grinder, of course. Fortunately in the last few years this is wayyyy more accessible. There are pretty good options starting around $300, and the workflow isn't terrible for these picks, either. Of course the sky is the limit here, but it's really vital to a good cup.

3) Good water. You'll want to either find a bottled water brand you like for brewing, or use an reverse osmosis (can be a gravity type) system and remineralize it. Cafes do this (if they are any good) and you should too. There's a chance your tap is great for coffee, but only if you're pretty lucky.

4) Decent brewing equipment. The cheapest is a v60 for pour over. You can make good coffee with pretty much any machine, but some will get in your way and cause you to have to fuss with them much more.

Then, after those, is technique - and the most important part of technique is really grind size and water temperature (I suggest you do not go above 88c in most cases).

The HTTP 418 I'm a teapot status response code indicates that the server refuses to brew coffee because it is, permanently, a teapot. A combined coffee/tea pot that is temporarily out of coffee should instead return 503.

> "It takes more than 150 people to make a cup of coffee, from farmer to barista."

I do not, nor have I ever, utilized the services of a barista. I make coffee at home or I purchase it from Wawa, Sheetz, 7-Eleven, whatnot.