As the manual-brewing trend has developed over the past few years, various coffee-making tools have emerged on the market. Some are classic methods that have been around for decades, others are brand new to the market (often in more ways than one), while still others are new versions of older methods.
When critically analyzing filter-coffee brewing devices and methods, I usually start with a set of assumptions:
1) Materials and design that promotes a stable brew temperature is best
A brewing environment will, for most brew methods, lose temperature naturally as heat dissipates to the surrounding air and materials that it comes in contact with (the exceptions are methods that add heat energy during the brew, such as vacuum/siphon or machine-drip). Certain materials serve as effective insulators (such as air and plastic) that slow this temperature loss, while others can serve as "heatsinks," which by their nature will transfer heat outward (glass, ceramic, metal).
So the material that the brewing space comes into contact with matters. Even if you "preheat" a dripper, it's going to be fairly impractical to actually get it to a high enough temperature to mitigate its heatsink action during the brew. The alternative is a design that reduces the physical contact that the brewing space has with the dripper material.
2) a design and method that promotes even extraction is best
When brewing coffee, "even extraction" is a simple idea that, in practice, is actually extremely complicated. In manual brewing it's really managing the amount and degree of unevenness. Because at some point, you need to separate the coffee grounds from the resulting beverage, it's pretty much impossible to achieve a truly even extraction.
For manual brewing, "even extraction" can be best managed by optimizing pour, flow, and geometry.
By "pour," I'm referring to the action of pouring water upon the coffee bed. I believe that reducing the "pour" down to ZERO should be the goal when brewing drip coffee. To explain this, let me explain "flow."
By "flow," I'm referring to the action of water flowing through the coffee bed. The flow of water through the bed (due to gravity) creates a lot more effective turbulence than most would assume. Remember, the coffee grounds are being held in place by the filter, which means the water is flowing past the grounds. When do you directly experience more turbulence: when you're floating in an inner-tube down a river, or when you're trying to stand still in that river?
So if the coffee bed is experiencing a certain amount of turbulence due to the flow of water, what about the pour? How does the amount of extra turbulence you create by pouring water on the top of the coffee bed change the evenness of turbulence? How does the depth of the coffee bed affect this unevenness?
This is why I stated that reducing the "pour" down to ZERO should be the goal when brewing drip coffee. If you're still with me, you might be realizing that NO brewer available actually works this way.
By "geometry," I'm referring to the shape of the brewing space, and how water flows through the bed and through the system.
A conical or wedge-shaped geometry will not brew very evenly. Just like a piece of meat won't grill evenly unless its top and bottom run parallel, the shape of a brewing space is very important.
Okay. Those are my assumptions. Moving forward.
This is why I'm encouraged by these two brew methods we've started importing from the KALITA company in Japan.
The Wave Series drippers provides a flatter bottom geometry than the others on the market, with the brew water flowing down through the bed and out the bottom. This first quantity are Kalita's 185-size, which is comparable to the 02-size for Hario V60 drippers and a Melitta #2. We will soon be bringing in the smaller 155-size drippers and filters. Why smaller? The smaller the filter, the smaller the distance of your pour.
The other unique design feature is the Wave filter. Because of the wavy-sidewalls, there is minimum contact between the brewing space and the dripper sidewalls. The filter actually "floats" in the dripper and doesn't touch the bottom of the dripper.
The Kantan Drip from Kalita is something truly special. Their main downside is that they only hold about 16 grams of coffee grounds. More than that, and you'll be overflowing after the bloom. Other than that, they're pretty badass. They're flat-bottomed as well, but because they're so small, you can actually pour with zero pour distance: you can actually place the tip of your pouring kettle on top of the bed of coffee as you pour. It's really as even as drip brewing gets, and in a origami-type fold-out design, which starts and stores flat. Oh, and there's effectively no "dripper" involved to steal heat.
I wanted to introduce these to the North American market because they have unique qualities which I think make them viable options for the pourover enthusiast. You may notice that they're a little more expensive than some of the others out there, but Kalita is, both here and in Japan, a premium product designed by and for coffee-professionals. What that means to you and me is that they make it easier to make consistently good quality brews. Isn't that what we want?