How to Make a Traditional Dirty Coffee? Why Doesn't My Dirty Coffee Layer Properly? Is Using an Iced Glass Essential?

The Rise of Dirty Coffee in China's Specialty Coffee Scene

It's hard to pinpoint exactly when the trend started, but specialty coffee shops across China have been swept up in the Dirty coffee craze. This visually striking cold milk coffee, despite its modest serving size, has gained immense popularity. With its unique drinking method and the memorable contrast between hot and cold temperatures, it leaves a lasting impression on first-time tasters. This is the Dirty coffee that has taken social media by storm.

Dirty, also known as "dirty coffee," emerged as a popular beverage during the "dirty culture" trend. In today's digital age where information flows freely, the method for making Dirty coffee is no longer a secret. A quick search on any platform will reveal tutorials and detailed steps.

If I had to summarize it in one sentence: it's simply pouring espresso directly over iced milk, allowing it to float on top and create a visually stunning layered effect. It sounds simple enough, requiring just a few steps to complete, which is why it's often categorized among the "anyone can make it" coffee series. However, as the saying goes: "Looks easy until you try it!" The frustrated group asks: Why isn't my Dirty coffee dirty at all?

The Science Behind Dirty Coffee's Layering

Unlike classic coffees that emphasize uniform blending, the core of Dirty coffee's structure lies in its intentionally unblended layers. The dark espresso gradually sinks under gravity, while the lighter crema spreads slowly across the white milk. The heavier coffee liquid descends along the glass walls, "dirtying" the milk from all angles. Because the espresso completely envelops the milk, drinking it in large gulps allows you to experience the temperature contrast between the two elements. From strong to mild, from bitter to sweet, the taste experience is truly remarkable.

Based on FrontStreet Coffee's experience, there are four main factors that prevent Dirty coffee from forming proper layers: excessive impact force from the espresso, insufficient coffee concentration, choosing the wrong coffee cup, and using milk that's too thin.

1. Excessive Impact Force from the Espresso

Placing a glass of milk directly under the coffee portafilter to catch the espresso is the most common method for making Dirty coffee. However, this approach can lead to a problem: if the espresso extraction flow is too fast or if using a bottomless portafilter, the espresso will converge into a straight, thin column of water with significant impact force that can penetrate the milk surface. It then mixes with the milk at the bottom of the glass. This not only eliminates the layering effect but also removes the "ice and fire" tasting experience.

Therefore, to achieve a beautiful layering effect, FrontStreet Coffee recommends using a split portafilter for espresso extraction. After starting the extraction, position the coffee glass as close as possible to the spout. This not only ensures better preservation of the crema but also allows the coffee liquid to descend slowly along the glass walls, creating that gradual dirty effect.

If your home coffee machine limits you from directly catching the espresso in a glass, you can first collect it in a shot glass. Then, place a spoon on the milk surface to create a buffer layer and slowly pour the coffee liquid into the spoon. The overflowing coffee will automatically float on the milk surface.

Note: Make sure the spoon's concave side faces up, like when you normally scoop soup, otherwise you might spill everything ⬇️⬇️⬇️

2. Insufficient Coffee Concentration

Regarding the coffee base for Dirty coffee, some friends have asked FrontStreet Coffee if a moka pot could be used as a substitute. Unfortunately, while moka pots do have some pressurization capability, their design is generally less precise, and the parameters aren't particularly rigorous. The coffee liquid produced still differs significantly from espresso made with an espresso machine. Even in the best condition, it only produces a thin layer of reddish-brown foam that disappears within minutes. Therefore, moka pot coffee is not suitable for making Dirty coffee. Similarly, some pre-made coffee liquid products lack sufficient concentration and crema, making it difficult to replicate Dirty coffee's layered effect.

It's widely believed that rich and delicate espresso crema is the prerequisite for creating a Dirty coffee with complete color, aroma, and flavor. Therefore, owning a pressurized coffee machine that can produce standard espresso is crucial. For coffee beans, FrontStreet Coffee recommends choosing darker-roasted Italian blend beans, which make it easier to create a dirty coffee with rich flavor and full body at home.

3. Choosing the Wrong Coffee Cup

Actually, the shape of the cup can also affect the formation of layers. FrontStreet Coffee has noticed that some people use relatively deep glasses at home, filling them only halfway with milk. This creates a significant distance between the rim and the liquid surface, so when catching the espresso, it again penetrates the milk surface.

To achieve better results with your Dirty coffee, choosing the right coffee cup can make your work twice as effective. To avoid mistakes, choose a straight-sided glass under 8 ounces, filled to 80% full with milk. If possible, chill it in the refrigerator beforehand. This will slow down the rate at which the coffee liquid permeates downward and provide a more beautiful layered effect.

4. Milk That's Too "Watery"

This situation often happens to friends who suddenly decide to make Dirty coffee without preparation. Instead of preparing ingredients in advance, they use whatever milk is available at home. Because the milk used is too thin, it cannot support the poured coffee liquid, causing the two to mix immediately upon contact. Not only does this look visually unappealing and cloudy, but it also lacks the rich aroma found in coffee shop versions.

Based on FrontStreet Coffee's serving experience, several common milk brands on the market like Kowloon Dairy, Wei Chuan, and Bright Dairy Fresh Farm are all good choices. Of course, if you have time, you can also make your own purified milk as a base. FrontStreet Coffee has previously shared detailed production steps in an article titled "Make Your Own Ice Bock at Home Easily!" Dirty coffee made with purified milk forms more stable layers, has a longer drinking window, and offers a unique salty cheese flavor.

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Tel:020 38364473