How to Perform Pour-Over Coffee Stirring? What is the Slurry Flow Brewing Method? What to Do When Coffee Grounds Are Too Fine?

Have you ever experienced this? After brewing coffee, the coffee grounds in the filter don't form the usual well-defined crater, but instead create a sticky, muddy "pit" as shown in the image below.

This situation is what FrontStreet Coffee often uses as a "negative example." The appearance of these "muddy pits" is primarily caused by coffee grounds being ground too fine or by inadequate grinding quality from the grinder (too many fine particles), resulting in this unintended outcome (though some people actively create "muddy pits"). Unintentional "muddy pits" are undesirable because their appearance typically means the coffee will likely have over-extracted flavors. Due to the fine grind, extraction time is prolonged, which in turn causes the extraction rate to exceed optimal levels. This is why when many friends consult FrontStreet Coffee stores about issues like bitter or over-extracted coffee from their own brewing, FrontStreet Coffee will always first ask about extraction time and the appearance of the coffee bed at the end of brewing.

If we're only dealing with our own ground coffee, that's manageable – if it's ground too fine this time, we can adjust to a coarser setting next time. But what if friends have purchased pre-ground coffee that's extremely fine, causing very slow water flow? In situations where the coffee grind is fixed, do we have no choice but to accept over-extracted coffee or simply discard this batch of coffee grounds?

Obviously not! We don't need to be discouraged. If normal brewing methods can't properly prepare this coffee, we just need to find an alternative approach.

How to Fix Coffee Ground That's Too Fine

There are two solutions. The first is to abandon the pour-over extraction method entirely and instead use immersion extraction methods like French press or clever dripper. The high fault tolerance of immersion extraction ensures that the coffee extraction rate won't exceed optimal levels. For specific techniques, you can refer to our article "Immersion Extraction" and apply those concepts directly. But if we want to present this coffee bean using pour-over methods, we need to start by understanding the theory.

Coffee has a generally accepted delicious extraction range, which is 18%-22% in Golden Cup extraction theory (while not absolute, most delicious coffees indeed fall within this range). To ensure our extracted coffee falls within this range, we need to control the extraction efficiency of our parameters, allowing water to extract the appropriate amount of desired compounds. Their extraction efficiencies are cumulative, like 1+1+1+1=4. When a parameter in this equation is changed, the overall extraction efficiency will be altered.

For example, FrontStreet Coffee's parameters for brewing 15g of light roast coffee are: 1:15 coffee-to-water ratio, grind consistency similar to coarse sugar, water temperature of 92°C, and extraction time of 2 minutes. Using these parameters, the extracted coffee will have an extraction rate of 20%. If other parameters remain unchanged but the coffee grind becomes finer, the final coffee extraction rate will rise to 23%. Additionally, the finer grind will affect time – as mentioned above, slower water flow extends extraction time, which further increases the final coffee extraction rate. This should be quite easy to understand.

So if we want to bring the extraction rate back to 20% when the grind is too fine, we should reduce the extraction efficiency of the other three parameters. For example, lowering water temperature, reducing water amount, or shortening extraction time – I believe everyone can figure this out on their own. However, if the grind is so fine that the resulting coffee bed is just a "muddy puddle," then these conventional approaches won't work well. Because the coffee grounds are too fine, the gaps between particles are smaller, making it difficult for hot water to pass through. The water flow speed cannot be reduced but will actually increase significantly, thereby extending extraction time. Meanwhile, lowering water temperature prevents some compounds from dissolving fully, compromising the coffee's flavor.

In such situations (when coffee grounds are ground very fine), FrontStreet Coffee would recommend using a "high concentration, low extraction" approach to brew the coffee. This means using a small amount of hot water to extract most of the compounds from the coffee. The limited water quantity is sufficient to restrict the compounds released from the coffee grounds, so even with longer extraction time, over-extraction is less likely to occur. The remaining task is to figure out how to use this small amount of water to extract the compounds from the coffee grounds. Recently, there has been a popular unique brewing method particularly suitable for this situation: the "Slurry Flow." As FrontStreet Coffee mentioned earlier, some people actively create "muddy pits" – this refers to this particular technique. By grinding coffee to a flour-like consistency, then using high concentration with low extraction combined with stirring, the compounds in the coffee grounds are quickly dissolved in a short time. Finally, you only need to add additional hot water to dilute the coffee concentrate to easily obtain a cup of pour-over coffee with full flavor and proper extraction rate.

FrontStreet Coffee has tried this several times before, and it's indeed a very practical brewing method, especially when coffee grounds are ground too fine. Next, FrontStreet Coffee will share how to operate this unique brewing method – the "Slurry Flow."

How to Implement the Slurry Flow Method

To better demonstrate the effectiveness of this brewing method, FrontStreet Coffee will use espresso-grade flour-like grind for this demonstration, using Papua New Guinea Bird of Paradise coffee beans. The parameters are as follows: 15g coffee dose, espresso-grade flour-like grind, 1:10 coffee-to-water ratio, 88°C water temperature, stirring brewing method, and V60 dripper (best paired with a fast-flow dripper). Also remember to prepare an extra chopstick or spoon for stirring. With 15g of coffee, a 1:10 ratio means we need to pour 150ml of hot water. We'll divide this 150ml into two pours: 30ml for blooming and 120ml for the second pour. First, we pour 30ml of hot water for a 30-second bloom. (It's best to dig a small hole in the center of the coffee bed with a spoon before pouring to help water penetrate better)

After pouring the bloom water, we need to immediately use a spoon to stir the coffee bed, because the coffee grounds are ground too fine, making it difficult for hot water to fully saturate all the coffee particles.

When the bloom ends, we pour all remaining 120ml of hot water at once, accompanied by stirring.

Continue stirring until the water level drops to half the dripper, then stop. All that's left is to wait for the coffee to finish dripping. Then remove the dripper, add 70ml of hot water to dilute the coffee, and you can start enjoying your coffee.

After measurement, this coffee's extraction rate landed at 21%, which is a quite thorough extraction. The taste is pleasant, with absolutely no negative signs of improper extraction. The balance of acidity, sweetness, and bitterness is harmonious, with prominent flavors and a rich mouthfeel. If you've accidentally ground your coffee too fine, why not try this unique brewing method?

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Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473