Nav: Home > Coffee >

What Causes Clumping in Espresso Crema? Pay Attention to These Details When Extracting Espresso!

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, The "golden armor" of espresso--Crema, is a wonderful product unique to pressurized extraction. Its presence not only provides an excellent "canvas" for coffee latte art but also makes the coffee taste richer and fuller. Of course, as FrontStreet Coffee often says, this is on the premise that the crema quality is up to standard.

The "golden armor" worn by espresso—the Crema—is a wonderful product unique to pressurized extraction. Its presence not only provides an excellent "canvas" for coffee latte art but also makes the coffee's texture more mellow. Of course, as FrontStreet Coffee often says, the prerequisite is that the quality of this crema must be up to standard! When the crema is too thick or too thin, it will significantly diminish its effects.

Recently, FrontStreet Coffee has received many inquiries from friends who find that while the espresso crema they use for milk coffee is thick, it lacks fluidity, much like whipped cream, appearing overall very "stiff"! Such crema not only affects the drinking experience but also creates obstacles when making latte art! This situation is likely caused by the following factors:

1. Operational Issues

Operational issues are one of the more common factors for this problem! After extraction is complete, the crema and coffee liquid remain closely integrated for a period of time. We can clearly observe by gently shaking that all the crema flows with the movement of the coffee liquid—very smooth! At this point, the espresso is most suitable for drinking and making other espresso-based drinks.

Freshly extracted espresso with smooth crema

However, if we don't use the espresso immediately after extraction but instead start doing other things, this layer of crema will not only dissipate over time but also separate from the coffee liquid. When we shake this cup of espresso then, we can observe this phenomenon: (pretend this is a GIF—the coffee liquid moves while the crema stays still)

Espresso with separated crema and coffee liquid

Although the coffee liquid at the bottom rotates with the shaking, most of the crema on top remains stationary except for the thinner parts that might jiggle slightly! Crema in this state is not very suitable for making hot milk coffee because the crema is too stiff, and light milk foam cannot push it, making it impossible to create beautiful latte art patterns! Therefore, we should use the espresso immediately after extraction is complete. Of course, if we miss the golden time of the espresso due to other delays, causing the crema to harden, we need to stir it at this point to reconnect the crema with the coffee liquid, giving it better fluidity.

2. Material Issues

What materials do we need to make a cup of espresso?

That's right! Coffee beans and water. When certain substances in these two materials are excessive, it will lead to extracted crema that is too hard and lacks fluidity!

FrontStreet Coffee has mentioned the issue of coffee beans many times, so clever friends can probably guess the root of the problem—that they're too fresh!

When beans are too fresh, they contain enormous amounts of carbon dioxide! Carbon dioxide and the lipids in coffee beans are the main components that form crema. When there's too much carbon dioxide, the lipids in coffee beans cannot encapsulate it for long periods. Therefore, within a short time after extraction, this crema will quickly rupture due to the activity of carbon dioxide, forming "clumps" that lack fluidity. In such cases, FrontStreet Coffee recommends solving this through pre-grinding—that is, grinding the coffee powder in advance and letting it sit for a short period to degas, just a few minutes! After being ground into powder, coffee beans will have stronger degassing capabilities due to the increased surface area, quickly releasing carbon dioxide to solve the problem of overly hard crema caused by rapid foam collapse. However, it's important to note that you cannot let it sit for too long, as the rate of gas loss after grinding is absolutely unimaginable!

Then there's the water used in the coffee machine! In the article "Preparing Coffee Water," FrontStreet Coffee explained why tap water cannot be used in coffee machines—because it contains too many minerals, which can place a certain burden on the coffee machine! Besides this, another reason not to use tap water, also caused by minerals, is that tap water has too high a KH value!

The KH value refers to the concentration of bicarbonate (HCO3-) in water, and bicarbonate is a very important buffering substance in water quality. Although it's important, moderation is key in everything! When the KH value in water is too high, the carbon dioxide in the coffee powder will be extracted more easily (as will other substances). If you happen to be using beans rich in carbon dioxide at this time, the result will be consistent with what was mentioned above—although the crema is abundant, it breaks more easily! At the same time, water quality will also have a certain impact on the taste of the espresso itself. In such cases, FrontStreet Coffee recommends installing a filtration system for the coffee machine water or changing the water source to solve this problem.

3. Parameter Issues

To give coffee more possibilities, we often use different parameters to extract espresso, thereby giving coffee a deliciousness that differs from the conventional (deliciously different). Water temperature, pressure, output volume, and grind are all adjustable parameters for espresso! Short-extracted Ristretto, long-extracted Lungo, or variable pressure/over-extracted espresso, etc. These are all delicious coffees made through parameter adjustments. However, if when adjusting these parameters, we make their extraction efficiency too prominent, it will cause large amounts of carbon dioxide to be extracted in a short time. At this point, due to the unstable structure of the crema, the aforementioned problems of excessive hardness and clumping can easily occur.

The taste of the coffee itself is not problematic, but the presence of the crema will bring certain negative effects! In such cases, besides stirring, friends making Americano can also remove some of the crema using filter paper or a filter screen to give the coffee a cleaner taste. For friends making latte art who encounter "harder" crema, FrontStreet Coffee recommends pre-mixing to obtain a high-fluidity coffee base! The specific operation is to add a little milk before mixing, then shake it evenly to give the crema more fluidity. This way, you can solve the problem of difficult latte art caused by overly hard crema!