What is a Double-Chamber Filter Paper? How to Brew Coffee with "Mandarin Duck Pot Filter Paper"? How to Make Pour-Over Coffee?

Getting to Know the "Dual Chamber" Filter Paper

New coffee gear seems to pop up all the time. Beyond the ever-evolving beans themselves, these fresh tools are what excite us most at FrontStreet Coffee — they open up entirely new ways to brew and make the whole experience more fun.

Lately, our attention has been captured by a filter paper released last year, because its design is genuinely unlike anything conventional. How unusual is it? It lets you brew a "dual chamber" pour-over. When unfolded, the paper has two separate compartments for coffee grounds, and since the shape resembles the divided "mandarin duck pot" used in Chinese hot pot, netizens have jokingly nicknamed it the "yuan yang pot filter paper."

Its official name is the "Dual Chamber Filter," made by the Spanish coffee equipment manufacturer Sibarist. What sets it apart from ordinary filter paper is the "partition wall" running down the middle, splitting the filter space in two. From the company's official videos, we at FrontStreet Coffee noticed that this divider is made of a much denser material, so hot water poured on one side during brewing can hardly seep through to the other. It really does behave like a wall. Naturally, we were ready to order a pack — until we saw the price...

Thirty sheets cost €37.44 — roughly 283 yuan, or about "9.4" yuan per sheet. Stop and think about how many bags of coffee beans that could buy!

Little wonder there are barely any reviews of this paper online. For a disposable consumable, that price is frankly outrageous, and out of reach for most regular drinkers. So if, like us, you're hesitating over whether to spend that much on filter paper, why not first build a budget-friendly replica and see whether this "dual chamber" paper is really worth the premium?

Making a Budget-Friendly Replica

The DIY version couldn't be simpler: take two size 01 filter papers and use them in a size 02 conical dripper. Fold both papers as you normally would, then insert them face-to-face into the dripper — and there you have it, your budget "dual chamber filter paper."

If you want better isolation — closer to the official version, whose divider keeps brewed coffee from seeping across — you can use non-woven filter material, because untreated filter paper is quite hard for liquid to penetrate when it isn't in contact with coffee grounds.

What to Keep in Mind When Brewing with the "Dual Chamber" Paper

Once we had replicated the paper, we ran into far more complications than expected. Picture it for yourself: how exactly should you brew with such an unusual filter?

The obvious purpose of the "dual chamber" design is to brew two beans with different characteristics — different roast levels, say — together in a single brew. After all, if the beans were similar, you could simply blend them dry and brew as usual; there would be no reason to keep them apart. But beans with different personalities call for different extraction parameters, and the parameter you have to solve first is water temperature.

Since you can't adjust water temperature mid-brew, brewing two beans with a big roast-level gap means you'll need at least two kettles — ideally temperature-controlled ones, otherwise managing the temperatures becomes a real hassle. That's the first hurdle.

With temperature solved, the brewing itself becomes the main challenge. Because you're brewing two different beans at once, you have to keep switching kettles throughout the pour. And you'll need solid arithmetic, too: both sides share one dripper and one scale, so every pour is cumulative.

That means you must work out the full brewing plan in advance, or you'll easily drift off your target coffee-to-water ratio. This is also why the "two-person pour-over" that netizens joked about in the comments (two people brewing one pot together) doesn't really work (unless you resort to some improvisational method). Those are the key things to watch for with this unusual paper — general guidance only; adjust to your actual brew. Next, FrontStreet Coffee will demonstrate the specific brewing method we used, purely for reference.

How FrontStreet Coffee Brewed with the "Dual Chamber" Paper

Since the two coffees will mix directly in the server — effectively a blend — you need two beans whose flavors and textures complement each other. The blending principles we've shared before come in handy here. We tried three combinations and had customers and friends in the shop taste them all. The crowd favorite was Mozart paired with Kaffa (13g Mozart, 7g Kaffa). Parameters: grind size — Mozart at EK43 setting 9.5, Kaffa at EK43 setting 10; water temperature — Mozart at 90°C, Kaffa at 92°C; coffee-to-water ratio — 1:15; pour structure — three-stage pour; dripper — V60 (size 02).

Once everything was set, we started with the Kaffa side: a 20ml bloom with 30 seconds on the clock (timer starts the moment you pour).

At the 20-second mark we began blooming the Mozart side, so that by the time we finished pouring for Kaffa, Mozart's bloom would also be complete. That bloom took 25ml, bringing the scale to a cumulative 45ml.

As Mozart's bloom water finished, the clock hit 30 seconds — time for Kaffa's second stage, 50ml (scale now at 95ml). Because the dripper space is divided, we poured with a reduced flow from a higher position to give the coffee adequate agitation. Once done, the other side had finished blooming, so we switched kettles again for Mozart's second stage, 100ml (scale at 195ml); then switched back for Kaffa's final stage, 35ml (scale at 230ml); and finally swapped kettles one last time for Mozart's closing pour, 70ml (scale at 300ml). At that point, the brew was complete.

Total brew time: 2 minutes 15 seconds. The cup's core flavor was still Mozart itself, but with Kaffa in the mix the complexity improved noticeably, and the body came through rounder and cleaner. (Genuinely tasty.) Still, for all that the final cup was rewarding, the preparation from start to finish was exhausting — managing two water temperatures, picking the beans and their ratio (a few lucky customer friends got roped into taste-testing; we'll dare to do it again next time ), tracking every pour against the running total on the scale... no joke, it's a lot of work. Unless you pick two beans that are close in roast level and processing method — allowing one shared water temperature — the whole thing gets much simpler. But as we said earlier, if you're choosing beans that similar, you might as well blend them and brew normally.

Then again, maybe we simply haven't unlocked the full potential of this paper yet. So go ahead — imagine, experiment, and see what else this special "dual chamber" filter paper can do.

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FrontStreet Coffee Recommendation

Since this dual-chamber brew pairs two beans with contrasting personalities, we recommend starting with FrontStreet Coffee's Ethiopia Yirgacheffe Guodingding — a bright, entry-level washed bean with vivid citrus, berry, and floral notes and a green-tea-like finish, the go-to first stop for anyone exploring specialty pour-over.

For the second chamber, FrontStreet Coffee's Mozart is a natural match: an Ethiopian bean prized for its raisin-toned sweetness and rich tropical fruit character. As in our demo above, pairing Mozart with another complementary bean at slightly different grind settings and water temperatures (90-92°C, a 1:15 ratio, three-stage pour) is exactly the kind of experiment the V60 was made for.