Coffee handling during blooming: should the outer grounds be wetted?
Tests across light, medium, and dark roasts found that whether the outer ring of grounds gets wet during blooming depends on one goal: letting all the coffee absorb water and release gas as evenly and quickly as possible. Skipping the outer ring often leaves extraction uneven, and light and medium roasts can turn grassy and green in the cup.
Pouring straight onto the outer ring can block the center from degassing, so the practical middle ground is a spiral from the center outward plus a gentle swirl or stir. After blooming, the experiments used the same two-pour extraction and identical technique, whether brewing in a dripper or making coffee in a coffee pot, so the pouring range was the only variable.
In the practice of pour-over coffee, one frequently discussed detail is: should the outer ring of coffee grounds be pre-wetted with water? This article starts from the two stages of blooming and formal extraction, and combines comparative experiments across light, medium, and dark roast levels to analyze the impact of pouring range on flavor. Experiments show that whether to wet the outer layer of grounds during blooming hinges on whether all coffee grounds can evenly absorb water and release gas in the shortest possible time. Not pouring around the outer ring tends to cause inconsistent extraction rates, and light and medium roast beans easily develop a green, grassy taste; while pouring directly onto the outer ring may block the central degassing. The article also shares practical techniques such as swirling and stirring to help coffee enthusiasts extract every particle of coffee more evenly.
Having watched a large number of instructional videos and personally brewed countless cups of coffee, you must already be quite familiar with pour-over coffee. However, have you ever struggled with this question: should the outer ring of coffee grounds be poured with water? During blooming, does the water stream need to go around to the outer ring?
To address this question, today we plan to discuss it from two perspectives.
§1|The Blooming Stage
Typically, the blooming pour in pour-over coffee starts from the center and spirals outward. So here's the question: should we pour water directly to the outer ring to fully saturate the coffee grounds, or only pour in a small area at the center and rely on natural diffusion to wet the outer ring? What difference do these two approaches make to the final flavor? With this question in mind, let's conduct an actual test.
This experiment uses coffee beans at three roast levels—light, medium, and dark—to investigate the flavor differences caused by whether the outer coffee grounds are wetted during blooming. Three roast levels were chosen because beans of different roast degrees differ in degassing and water absorption rates, making it easier to observe changes in the blooming state.
For the brewing stage after blooming, a standard two-pour extraction is uniformly adopted, and the pouring technique is kept consistent.
test 1: Sidamo Flower Queen, light roast
test 2: Yemen Mocha Mattari, medium roast
test 3: Sumatra Golden Mandheling, dark roast
In the first two test groups, the approach of not pouring around the outer ring during blooming resulted in a grassy green flavor as well as the astringency and sourness caused by under-extraction; while the third group was not noticeably affected (dark roast coffee degasses quickly, and water passes through the grounds faster).
Through tasting comparison, it was found that whether the outer grounds layer is wetted during blooming mainly affects flavor at the extraction preparation stage, due to uneven extraction caused by the time difference in water absorption among coffee grounds. The core purpose of blooming is to quickly saturate all coffee grounds so that all particles can evenly absorb water and degas within as close a time frame as possible.
In the group where the outer ring was not poured around, water permeates from the center outward. By the time the central coffee grounds have reached a saturated state, the outer grounds have only just come into contact with water, which leads to inconsistent extraction rates—especially for light and medium roast beans, which exhibit a green, astringent taste and under-extraction.
But if the blooming pour goes around to the outer ring, another phenomenon appears: water permeates from the outside inward, the central coffee grounds' outward degassing is blocked, and the gas is forced to escape upward, making it look as though the bloom has failed.
The key to pouring at the center is to wet all coffee grounds as quickly as possible. As long as this goal of speed can be achieved, the difference between a small-area pour that permeates to the outer ring and a direct pour that soaks the outer ring is actually not significant, and appropriately extending the blooming time can also compensate for an insufficient bloom.
It should be noted that when blooming with a central pour, if small bubbles keep emerging from the same spot, it indicates that area is not blooming sufficiently—the force of the water failed to reach the coffee grounds at the bottom, and permeation was blocked by the coffee grounds' degassing. Subsequently, you can use a fast and forceful spiral pour and stirring to make the bottom coffee grounds tumble, thereby improving the extraction yield.
§2|Handling of Outer Coffee Grounds During Formal Extraction
We have repeatedly emphasized in previous articles that during brewing you should not pour around the outer ring, to avoid pouring onto the filter paper—that is, the water stream breaking through the coffee bed and washing the filter paper, causing water to escape from the edge of the filter paper, which makes the brewed coffee weak and tasteless.
Pour in a spiral around the center, about the size of a one-yuan coin ↓
Pour around the outer ring ↓
Moreover, when the water stream hits the outer layer, it concentrates the coffee grounds toward the middle of the dripper, putting the coffee in a steeped state and lacking proper tumbling extraction, which easily gives the coffee a watery and astringent taste.
If you're worried that that little bit of grounds in the outer ring not being extracted will affect the taste, why not think about it from a different angle—why obsess over that small ring of coffee grounds?
Pouring water directly onto the outer ring is a relatively risky approach and is not recommended. You can use fast spiraling and a higher pour to create turbulence, folding the outer coffee grounds into the center, but be careful not to over-extract.
Finally, there are a few more tips for dealing with the outer coffee grounds: swirling and stirring. These two methods mainly target light roast or finely ground coffee. Through them, you can effectively ensure all the coffee is extracted. Swirling and stirring during blooming can accelerate coffee degassing and saturation, avoiding uneven or insufficient blooming caused by slow water permeation. And stirring during extraction and swirling at the end of extraction can increase the extraction yield (again, be careful to avoid over-extraction), speed up the flow rate, and prevent steeping for too long.
The above are some explorations and small suggestions regarding the handling of outer coffee grounds, and I hope they are helpful to everyone.
The above content is compiled by CoffeeHunters, a coffee news website.
