Introduction:Besides the common inverted brewing method, the AeroPress official guide also recommends using the upright (positive pressure) method for extraction. However, many users remain uncertain about which grind size to choose when using positive pressure. This article uses light to medium roasted beans as an example, testing three common grind levels to analyze their differences in aroma, acidity-sweetness balance, clarity, and body, helping you find the most suitable positive pressure brewing method for your taste.
The AeroPress is an extremely versatile coffee brewing device, and the most frequently mentioned method is the inverted technique. However, the officially recommended preferred method is actually the upright (positive pressure) approach. Compared to the inverted method, positive pressure is not only more intuitive to operate but can also produce a richer and smoother flavor through the application of pressure. Nevertheless, to achieve the best performance with positive pressure, selecting the right grind size is crucial. This article will use experimental light to medium roasted beans, trying out three common grind sizes—BG 5M, BG 5R, and BG 6M—to explore their performance and flavor differences under positive pressure extraction.
The experimental beans used in this test consist of 70% Guatemalan Geisha and 30% Catuaí and Caturra blends, roasted to a light to medium level, which helps preserve clear floral and fruity aromas. After brewing, notes such as citrus, peach, jasmine, honey, and tea-like qualities are often perceived. The characteristics of these beans make them well-suited for testing extraction performance under different grind conditions.
During the positive pressure extraction process, we kept the water temperature constant at 90°C, set the coffee-to-water ratio at 1:15, and used a total of 228 grams of water. First, 35 grams of water were poured in for a 30-second bloom, followed by additional pouring up to 125 grams for the first pour, then up to 228 grams before stopping. The coffee was allowed to steep until 1 minute and 30 seconds before pressing, with the full extraction time being approximately 1 minute and 48 seconds. This parameter setup is similar to a standard pour over routine, but because the water flow is slower during positive pressure, care should still be taken to avoid over-extraction.
The three grind sizes used in the experiment were: BG 5M (with about 60% passing through a Chinese standard No. 20 sieve), BG 5R (about 58% passing), and BG 6M (about 47% passing). These values roughly correspond to medium-fine, medium, and medium-coarse grind ranges in pour over brewing. Although no additional manual stirring was performed during the experiment, the natural agitation caused by the water stream was sufficient to mix the coffee grounds adequately.
The first test was with the finer BG 5M grind setting. The brewed coffee from this group exhibited pronounced jasmine floral notes, with a cup dominated by bright acidity of citrus and starfruit, accompanied by sweetness reminiscent of cane sugar and rice. However, the finish revealed some woody off-notes, and the overall clarity was slightly lacking—typically a sign of over-extraction due to the grind being too fine.
The second group used the BG 5R grind setting, which resulted in a more balanced performance. Its aroma was more subdued but still allowed for gentle floral notes to come through. The flavor profile was primarily citrus and orange acidity with sweetness, gradually transitioning to caramel and honey tones in the mid-palate, while the finish offered tea-like notes, nuttiness, and a creamy smoothness. This group exhibited clear layering, smooth mouthfeel, and was considered the most balanced option among the three.
Finally, the BG 6M coarse grind setting was tested. The coffee brewed with this group featured a bright acidity dominated by citrus and lemon notes, paired with aromas of brown sugar and cream, resulting in a flavor that leaned toward simplicity and freshness. The finish had a lemon black tea-like quality, with an overall clean profile, though the sweetness and complexity were slightly inferior to the BG 5R. However, the coarser grind helped avoid the risk of over-extraction.
Overall, the comparison shows that BG 5M, due to its overly fine grind, delivered bright acidity but tended to have woody off-notes and lacked clarity; BG 6M was clean and had clear acidity, yet lacked sufficient sweetness and complexity; whereas BG 5R excelled in acidity-sweetness balance, layered flavors, and overall smoothness, making it the recommended grind range for this experiment.
From this practical test, one useful conclusion can be drawn: whether you choose positive or inverted brewing, the grind size for the AeroPress can actually be referenced from common pour over ranges. Positive pressure brewing, due to the added pressure, often produces a thin layer of delicate crema on the coffee’s surface, resulting in a smoother mouthfeel and rounder aftertaste—this is part of its unique charm.
If you’re new to the AeroPress, you might want to start with a medium grind (similar to BG 5R) and then fine-tune based on the actual flavor profile. Remember, stable water temperature, appropriate bloom time, and proper pouring techniques will also greatly impact the final extraction quality. Through continuous experimentation, you’ll be able to discover the positive pressure brewing recipe that best suits your personal taste.
The above content is compiled by CoffeeHunters, a coffee news website.
