The Complete Guide to Cold Brew Coffee: Everything You Need to Know

Many coffee enthusiasts, including those at FrontStreet Coffee, have a habit when they first start brewing: observing the coffee bed after brewing. Why? Because we can identify areas in our brewing technique that might need correction by examining the "condition" of the coffee bed.

If the coffee bed forms a bowl shape with complete and evenly thick walls, it indicates that our water pouring technique during brewing is relatively standardized and doesn't require significant adjustments. However, if the coffee bed shows "abnormalities" such as uneven surfaces or pitted walls, it suggests our pouring technique might be less standardized and potentially needs correction. While improper pouring doesn't necessarily make coffee taste bad, it can potentially reduce the coffee's quality. For example, the coffee bed condition in the image below serves as an excellent illustration.

We can clearly observe that although the coffee bed walls have built up to sufficient height, there's a disconnection between the walls and the bottom of the coffee bed. It appears as if the entire coffee bed has been split into two sections. This is a phenomenon that many friends often complain about to FrontStreet Coffee! Even when they follow tutorial instructions for brewing and pouring, the final appearance of their coffee bed often shows this "cut-in-half" state. The resulting coffee flavor also falls somewhat short—it's not necessarily bad, but it just doesn't taste as good as it could.

This phenomenon typically occurs because water is poured directly onto the coffee bed walls, washing away the coffee grounds in those areas. This is precisely what puzzles many friends, because even though they clearly haven't poured water directly onto these walls, this situation still occurs.

Why Does the Coffee Bed Split in Two After Brewing?

This is quite an interesting phenomenon. In FrontStreet Coffee's previously shared article "Complete Guide to Hand-Poured Coffee Beds," this particular coffee bed formation was documented. There are two main reasons why this type of coffee bed occurs, typically happening during the final stages of multi-stage brewing. One reason is the direct pouring of hot water onto the coffee bed walls, as mentioned earlier, which washes away the coffee grounds on the walls. The other reason is due to excessive water column penetration force.

When we pour from too high a position or with too much water flow, the water stream will possess strong penetrating power. In this situation, even if we don't pour water directly onto the filter cup edges, the excessive penetration force can cause the water to break through the coffee bed walls hidden beneath the surface, creating the phenomenon where the coffee bed appears cut in two. The appearance of this phenomenon can cause both the extraction rate and concentration of the resulting coffee to decrease (there's a probability of this, and it's not small), because some of the hot water that breaks through the coffee bed walls falls directly into the lower vessel, creating bypass water. Not only does this reduce the amount of extracted substances, but it also directly dilutes the concentration of the already extracted coffee. Therefore, the appearance of this type of coffee bed indicates both improper pouring technique and a potential decrease in coffee quality.

How to Avoid Coffee Bed Separation?

The adjustment method is quite simple, with two approaches available that we can choose based on our current brewing situation. The first adjustment method is to reduce the pouring circle. This way, even with strong pouring force, we don't need to worry about the coffee bed walls being broken through, because the hot water will hit the thickest part of the coffee bed. Taking FrontStreet Coffee as an example, when using three-stage brewing, FrontStreet Coffee concentrates the final stage's hot water injection in the center. Circular motions are still performed, but with a radius only about the size of a coin. This serves not only to ensure hot water doesn't break through the coffee bed walls creating bypass water, but also to increase the extraction rate of the bottom coffee grounds, making the coffee extraction more uniform and the flavor expression more complete.

Another method is to reduce the intensity of the water flow. Since the coffee bed walls are being broken through due to excessive water flow penetration force, we can simply reduce the water flow intensity to solve this problem. As FrontStreet Coffee mentioned earlier, water flow penetration force is influenced by pouring height and pouring rate—the higher the pouring position and greater the water flow, the stronger the water flow penetration force. Conversely, if we want to reduce water flow penetration force, we only need to lower the pouring height or decrease the water flow.

When FrontStreet Coffee brews coffee, the water column height is typically maintained around 3-4cm (approximately the height of a fist). This isn't necessarily because this height produces the best-tasting coffee, but rather because brewing at this height has the smallest probability of accidents—in other words, it's a more conservative approach! This height ensures the water column provides sufficient agitation while avoiding excessive penetration force that would cause bypass water formation, making it easier to handle and very suitable for beginners just starting out.

Finally, FrontStreet Coffee wants to emphasize one point: whether the coffee bed looks aesthetically pleasing doesn't directly prove whether the coffee tastes good—it only shows your general pouring path during the brewing process. Therefore, it's best not to judge coffee flavor solely based on the appearance of the coffee bed. However, when we find that our brewed coffee doesn't taste as good as usual, the coffee bed can serve as another detail (besides parameters) to help identify problems. So FrontStreet Coffee's point is: everyone should first taste the coffee, and when the flavor doesn't meet expectations, then use the parameters and coffee bed appearance to identify the issue.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473