How to Create Layered Effects in Dirty Coffee? What's the Connection Between Bocca and Dirty?

Today, the Dirty remains an incredibly popular signature drink. However, many of us have encountered this problem: when making a Dirty, the espresso sinks very quickly into the milk, failing to create the distinct layered effect.

The layering of coffee and milk is the soul of the Dirty. Only through this layering can we experience the diverse layers this drink intends to offer. Otherwise, it simply becomes an iced latte without ice.

The Principle Behind Layering

The principle of layering is quite simple: the liquid placed at the bottom needs to have a higher density than the liquid above it. When there's a difference in density between the two, layering occurs. However, many factors can prevent this layering from happening. Today, let's analyze all the factors that might cause layering failure.

Coffee Liquid Concentration

Many friends might consider using coffee extracted from a moka pot to make Dirty due to various limitations. Unfortunately, coffee liquid extracted from a moka pot is not suitable as the espresso base for Dirty because its concentration and density are far below that of espresso extracted from an espresso machine.

Moreover, it cannot extract the golden crema of espresso. As we know, crema is an essential substance that preserves aroma and enhances the overall mouthfeel. Without it, not only is it difficult for the Dirty to layer, but it also loses a significant portion of its flavor experience.

Milk Temperature

Using room temperature milk is one of the most common reasons for failure because neither its density nor viscosity can match that of cold milk, making it easier for espresso to sink.

Additionally, in terms of flavor, it cannot compare to iced milk, significantly reducing the sweetness that milk contributes to a Dirty. It also fails to showcase the characteristic dual sensation of cold and hot that defines a good Dirty. Therefore, when conditions permit, using iced milk is always the best choice.

Distance Between Espresso and Milk

Another significant influencing factor is the excessive distance between the espresso and milk. This causes the espresso to have too strong an impact when poured, directly penetrating the milk surface, thus creating an "iced latte." Therefore, when pouring espresso, we need to reduce the impact of the falling espresso. The weaker the impact, the more thoroughly the espresso and milk can layer.

We can either position the milk directly against the group head's outlet during espresso extraction, or extract the espresso into a small pitcher and then use a spoon to block and drizzle it over the milk surface. If choosing the former method, you might try using a double shot extraction, which can create an incredibly beautiful Dirty! This perfectly interprets the origin of the name "Dirty": milk stained by coffee.

Cup Selection

Typically, we can see that coffee shops use short, wide-mouthed cups for Dirty, rarely using tall, narrow-mouthed cups like latte glasses. This is because a wider cup provides a broader liquid surface, allowing the milk to better distribute the weight of the espresso evenly, reducing pressure applied and achieving a more perfect layering effect.

The most important reason is that when drinking, it's easier to consume both coffee and milk together, avoiding the awkward situation of taking a large sip of espresso directly while leaving the milk at the bottom of the cup.

Achieving Even More Distinct Layering

Now that we understand that milk can layer with espresso mainly due to density differences between them, what should we do if we want even more distinct layering? To achieve a more perfect layering effect, we can try increasing the milk's concentration, further widening the density difference between it and the espresso, thus creating an even more absolute layering effect. In this case, using BOCK milk would be the best choice.

(Milk concentration measured separately with a concentration meter, showing that BOCK milk far exceeds ordinary milk) (BOCK milk preparation method) FrontStreet Coffee's previous article mainly discussed how to make higher concentration, more flavorful milk at home. The Dirty made with this milk offers an even more stunning taste experience. When you have time, just select a bottle of "lucky milk" and place it in the refrigerator. The next day, after the drip filtration is complete, you can make a rich, silky, and explosively sweet Dirty!

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FrontStreet Coffee (FrontStreet Coffee)
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