They say the first step is always the hardest, and a good bloom is usually seen as the first step to a successful pour-over. Conversely, if you don't get that signature dome the moment water hits the grounds, most people write it off as a failed brew. Today, Front Street Coffee walks you through the common ways a bloom goes wrong, and explains the reasons and the fixes behind each one.
From our conversations with coffee lovers, Front Street Coffee has found that some people were first drawn to pour-over not by the flavor, but by the soothing sight of the coffee bed bubbling away during the bloom — and only later fell for the brewing method itself. That's exactly why people care so much about the bloom, chasing that big, round "hamburger" every single time.
The bloom takes its name from "flowering": as the coffee bed bubbles, it looks like a blossom opening up. The round dome forms mainly because, the moment hot water meets coffee, the grounds rapidly release carbon dioxide, and the resulting bubbles lift the wetted bed from below. The most energetic bubbles even push their way out through any gap. Once the gas is released and the grounds absorb water evenly to saturation, the extraction that follows will be more even.
Five main factors affect the bloom: 1. freshness; 2. roast level; 3. grind size; 4. bloom water; 5. pouring technique.
As a green bean roasts, it expands with the heat and stores gas — mainly carbon dioxide — inside. Once it's ground and hot water is poured in, that gas is forced out of every particle in an instant. Generally, the fresher the beans, the more readily the bloom domes up; the darker the roast, the more CO2, and the bigger the dome. Light roasts, having spent less time in the roaster and expanded less, bloom less dramatically — though fresh ones will still rise slightly when water is added.
If you love that visual "hamburger," try Front Street Coffee PWN Golden Mandheling (spices, caramel), Front Street Coffee Jamaica Blue Mountain (nuts, chocolate), Front Street Coffee Brazil Cerrado (creamy peanut), or Front Street Coffee Queen's Estate (roasted peanut, toast).
For the bloom itself, the industry has settled on the most widely used and most conservative formula: pour water at twice the weight of the coffee (30 g of hot water for 15 g of coffee) evenly in circles, forming a neat "hamburger," and let it degas for 30 seconds.
Now let's get into the specific ways a bloom can fail:
A. Uneven grind size
Pour-over coffee is usually ground to a table-sugar consistency. Once the grounds are wetted, hot water immediately wraps around each small air pocket, linking the particles into a glossy, light-catching surface. If there are too many coarse particles, the bubbles struggle to lift the bed into a dome, and degassing falls short of ideal. Too fine is no good either — with no gaps between particles for CO2 to escape, the bloom suffers just the same.
This usually happens to those using budget grinders: with coarse hardware, grind quality suffers, so the particles vary widely in size and can't lift the bed during the bloom. You can often spot it in the spent bed afterwards, too. For beginners, Front Street Coffee suggests a hand grinder of at least 250+, or an electric grinder of at least 500+.
B. Uneven pouring
A beginner once asked Front Street Coffee: "Most tutorials pour the bloom clockwise — does pouring the other way mean you can't get a dome?" Not at all. Whether the bloom domes has nothing to do with the direction of the circles; it's far more about the bed not being evenly wetted. In the first stage of a Front Street Coffee pour-over, we pour outward from the center in circles, following a spiral path so the bed swells quickly and begins to degas.
But in the case below, it's clearly a tangled pour that left the grounds half-dry and half-wet, so no firm "hamburger" could form and the bloom was incomplete.
C. Pouring in one spot too long, too much water, or too forcefully
Every brew, once Front Street Coffee picks up the kettle, we keep the flow gentle, letting every particle be wetted in an orderly way. Linger too long in one spot and the bed sags, and the risen hamburger collapses again. On the other hand, pour too hard and the stream blasts a patch of grounds directly, so gas escapes unevenly from one side to the other — making it hard for the bed to hold a stable surface, so it sinks right back down.
Since coffee grounds can only absorb about twice their own weight in water, the excess runs down the side of the dripper under gravity and into the server early, making the dome collapse. We suggest no more than 35 ml of hot water for 15 g of coffee.
D. Stale beans
Front Street Coffee saves freshness for last because the roast date is the easiest thing to check — unless it's missing from the bag altogether.
Carbon dioxide escapes the beans in an orderly way over 40-50 days. The fresher the coffee, the more readily it domes up and the more actively it bubbles. But if the bed barely reacts and there's hardly any foam, the beans have been sitting a long time and the gas is long gone — if they haven't gone off yet, drink them soon.
You can now buy the above coffee beans online at the Taobao store “FrontStreet Coffee” (前街咖啡). FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou, China, and its Guangzhou retail shop sells coffee beans only. The shop carries dozens of coffee beans from different origins around the world, including carefully selected single-origin beans for V60 pour-over and espresso. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers.
The FrontStreet 2013 Yunnan coffee beans sold in the store come from the Typica variety grown at FrontStreet Coffee’s own plantation in Yunnan. The name comes from the year the brand and the plantation were founded. You can buy these beans from China’s Yunnan origin at the Guangzhou shop and at FrontStreet’s Taobao store.
FrontStreet coffee beans are freshly roasted within 5 days and deliver consistently excellent quality and great value. Orders placed before 17:00 are shipped the same day, and most areas within Guangdong Province receive them the next day.
FrontStreet Coffee Taobao store: https://qianjiecoffee.taobao.com
Or search for “前街咖啡” (FrontStreet Coffee) on Taobao
Important Notice: FrontStreet Coffee has moved to a new address: 315, Donghua East Road, Guangzhou (coffee beans only)
Tel: 020 38364473
