Dirty Coffee Layering Technique Tutorial: The Correct Way to Make and Drink Dirty Latte

What is Dirty Coffee?

What we commonly call Dirty coffee is essentially made by taking a glass, filling it with milk, and placing it under the espresso extraction head. The espresso slowly flows into the glass, causing the coffee to float on top of the milk, creating beautiful layers. Over time, the upper coffee layer gradually permeates the white milk, creating that "dirty" appearance.

Reading others' descriptions of Dirty coffee, it seems like anyone with hands could make it. But in reality, people often wonder: "Why doesn't mine have layers?" "My coffee layer sank to the bottom?" "It completely turned into milk tea color?"

What's the Difference Between Dirty and Iced Latte?

Dirty coffee and iced latte look quite similar - both are in a layered state when first made. However, the drinking experience is completely different. Iced lattes typically include ice cubes and more milk, and need to be stirred well before drinking. Dirty coffee, on the other hand, uses smaller cups and is generally consumed while still layered. First sip: rich coffee flavor; second sip: the aroma where coffee and milk blend; third sip: intense milky fragrance. It's an immersive experience.

How to Make a Dirty Coffee with Clear Layers?

The method for making Dirty coffee is no longer a secret, and the preparation is basically standard. FrontStreet Coffee won't go into detail about this. Instead, let's share the key details that FrontStreet Coffee focuses on when making Dirty coffee. If we boil it down to a formula, it's "extreme cold against extreme heat, both sides with matching concentration, and minimal impact force."

Dirty coffee is served without ice, so to maintain low temperatures, we need to approach it from other aspects. The cup and milk are the best choices. FrontStreet Coffee stores the cups and milk used for Dirty coffee in the refrigerator and takes them out when needed. Sufficient low temperature keeps the coffee more stable and prevents the Dirty coffee from becoming room temperature by the time it reaches the customer.

Both milk and coffee need to have high and similar concentrations. When two solutions with high and similar concentrations merge, their mutual permeation is relatively slow, creating stable layers. When the concentration of the bottom solution is significantly lower than the top solution, the top solution will quickly permeate into the bottom - the "sinking" phenomenon. When the bottom solution's concentration is significantly higher than the top solution, the layered structure becomes very firm - you can refer to ice blog Dirty coffee for this.

In other words, when milk is too thin, its quality can't support the coffee liquid, so it sinks, losing the layered effect. When milk is too viscous, the coffee can't penetrate, creating layers that are too firm, losing the "dirty" effect. This is based on espresso being in its normal state.

When milk is at normal concentration but the coffee is too thin, they also tend to permeate each other easily. To put it bluntly, this is because the overall concentration is low and the difference between the two is too great, plus the coffee has too much mass (high water content). Espresso rich in crema will float more easily on the surface because its weight is less than its volume - meaning it has less mass.

FrontStreet Coffee uses fresh milk with approximately 10.66% concentration, while espresso has about 9.88% concentration. The two concentrations are similar, and the coffee concentration is slightly lower than the milk's. This creates perfect "layering" when first made, and within 2 minutes, it achieves that "dirty" state as it moves downward.

The final point is to reduce impact force, whether when coffee flows into milk or when milk is poured into the cup. When choosing a cup, select an appropriately sized one. For example, when FrontStreet Coffee makes a 220ml coffee, we choose a cup between 220-240ml.

When pouring milk, try not to be too forceful. Excessive impact force can easily create bubbles on the milk surface. When receiving coffee liquid, the shorter the distance, the better. Let the coffee slowly flow into the glass and float on top of the milk. If you increase this distance, affected by gravitational acceleration, the layering effect definitely won't be as good.

The entire method emphasizes "gentleness" - and requires a bit of physics knowledge!

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473