Which Grind Size Works for AeroPress Standard Brewing?
For AeroPress positive pressure brewing, the grind can follow the range used for pour-over. A test using a washed Panama bean at three settings, BG 5M, BG 5R and BG 6M, all with the same water temperature, ratio and technique, showed the method forgiving across that spread. The finer settings pulled more sweetness and body.
Each cup was judged on aroma, acidity, sweetness and cleanliness. Positive pressure drains more slowly than an inverted brew, and pressing compresses air rather than the coffee bed, so the rubber seal interferes less with flavor. That pressure gives the oily mouthfeel and smooth texture that set the AeroPress apart.
The official recommended method for the AeroPress is actually positive pressure brewing, but many coffee enthusiasts are more familiar with the inverted method. So how should the grind size be chosen for positive pressure extraction? And what flavor differences do different grind sizes bring? In this article, we use [Front Street Panama Washed Butterfly] as the experimental bean, selecting three grind sizes—BG 5M, BG 5R, and BG 6M—and conduct positive pressure brewing comparisons under fixed water temperature, coffee-to-water ratio, and technique, evaluating each one by aroma, acidity, sweetness, and cleanliness. The conclusion is: just like the inverted method, positive pressure can also reference the grind range of pour-over, and the unique oily mouthfeel and smooth texture brought by pressure extraction are exactly the charm of the AeroPress.
We have previously compared the performance of the inverted AeroPress at different grind sizes. But the AeroPress is not limited to the inverted method—positive pressure is also an officially recommended brewing path. If we switch to positive pressure, how much impact will a change in grind size have on the flavor in the cup?
| Positive Pressure
The inverted method involves first flipping the device to perform immersion extraction, then pressing the coffee liquid out through the plunger; positive pressure, on the other hand, places the AeroPress directly on a server, completes the pouring and soaking, and then pushes the liquid out with the plunger.
During positive pressure extraction, the overall flow rate is on the slower side, but there will still be "leaking" where drips fall while pouring.
In actual brewing, positive pressure feels very much like a flat-bottom pour-over dripper, with the main difference being that without pressure, the water drains noticeably more slowly. Another difference from the inverted method is that when the plunger is pressed down, it mainly compresses air and does not directly contact the coffee liquid, so the rubber seal interferes relatively less with the flavor.
| Bean Information
The bean used in this experiment is [Front Street Panama Washed Butterfly], composed of 70% Geisha and 30% Caturra and Catuai. The light-medium roast preserves the floral and fruity character, presenting citrus and jasmine aromas in the cup, along with flavors of peach, citrus, honey, and tea.
[Front Street Washed Butterfly]
Country: Panama
Region: Boquete
Altitude: 1,600 meters
Processing Method: Washed
Variety: 70% Geisha, Caturra, Catuai
Roast Level: Light Roast
| Experiment
We selected three grind sizes for positive pressure brewing: BG 5M (60% passing rate on China standard No. 20 sieve), BG 5R (58% passing rate on China standard No. 20 sieve), and BG 6M (47% passing rate on China standard No. 20 sieve). Apart from grind size, the other parameters and technique were kept as consistent as possible. Since the water stream itself already provides agitation during pouring, no additional stirring was done.
Parameters and technique: water temperature 90°C, coffee-to-water ratio 1:15, first pour 35g of water for a 30-second bloom, pour and stir until 125g, then pause, continue pouring until 228g and stop, soak until 1:30 then press, total press-out time 1:48.
[BG 5M]
Flavor: jasmine in the aroma; on the palate, citrus and star fruit acidity, accompanied by sugarcane and genmaicha notes, but a woody off-flavor appears in the finish, and cleanliness is less than ideal.
[BG 5R]
Flavor: a faint floral scent on the nose; on the palate, the sweet-tartness of citrus and orange, transitioning to caramel and honey sweetness in the mid-palate, with a finish of tea, nuts, and creamy aroma. Relatively layered, smooth mouthfeel, and overall balanced.
[BG 6M]
Flavor: citrus and lemon acidity on the palate, with brown sugar and creamy aroma, and a finish reminiscent of lemon black tea.
| Summary
Among the three grind sizes, BG 5M produced coffee with a more pronounced woody taste and poorer cleanliness; BG 6M, while cleaner, had prominent fruit acidity but insufficient sweetness; BG 5R performed better in sweet-acid balance and was also relatively clean in mouthfeel.
From this we can conclude that whether using positive pressure or inverted, the grind size can reference the range of everyday pour-over.
Although the extraction parameters are close to pour-over, the AeroPress is a pressure extraction, and the pressed coffee has a thin layer of oil floating on the surface, with a certain smoothness on the palate.
The above content is compiled by CoffeeHunters, a coffee news website.
