To this day, Dirty is still a very popular star product. But I believe many friends will often encounter it: when making dirty, the espresso sinks into the milk very quickly, and there is no obvious layering effect.
The layering of coffee and milk can be said to be the core of Dirty's soul, and only when they produce layering can we feel the multi-layered layers that this cup of coffee has to bring us, otherwise, it is just an iced latte without ice. 
The principle of delamination is very simple, the density of the liquid placed below needs to be larger than that of the liquid above, and the density between the two is different, which can produce the phenomenon of delamination. But there are many reasons why stratification is not possible. Today, let's dissect how many factors can lead to the failure of layering1. The concentration of the coffee liquid
Many friends will want to use the coffee extracted from the Moka pot to make dirty due to various constraints, but unfortunately, the coffee liquid extracted by the Moka pot is not suitable as a concentrated base for dirty, because its concentration and density are far from the espresso extracted by the espresso machine.
Also, it can't extract the golden grease of espresso. It is important to know that oil is an important substance that retains aroma and enhances the overall taste, and without it, dirty is not only difficult to layer, but also loses a lot of taste experience. Second, the temperature of the milkChoosing milk at room temperature is one of the most likely reasons for overturning, because whether it is its density or viscosity, it cannot reach the size of milk at low temperatures, which will more likely lead to concentrated sagging.
Moreover, in terms of taste, it cannot be compared with ice milk, which greatly reduces the sweetness of milk in dirty, and cannot reflect the layering of dirty's hot and cold days. Therefore, it is best to use ice milk when possible. 3. The distance between concentrate and milk
There is also a larger factor: the distance between the espresso and the milk is too large, causing the espresso to punch too hard when poured and penetrate directly through the surface of the milk, thus creating an "iced latte". Therefore, when pouring into the concentrate, we need to reduce the impact of the concentration falling, the weaker the impact, the more thoroughly the concentration and milk can be stratified.
We can choose to concentrate the milk directly against the outlet of the brew head, or we can concentrate the milk in a milk cup and use a spoon to pour it on the surface of the milk. If you choose the former, you can try using double-ended extraction, which can extract super beautiful dirty!! A perfect illustration of the origin of the name Dirty: milk stained by coffee. Fourth, the choice of cups
Generally, we can see that the dirty cups used in coffee shops are low and wide, and it is rare to use a high and narrow mouth like a latte cup. This is because the wider cup has a wider liquid surface, and the milk is more able to evenly distribute the concentrated gravity, reducing the pressure applied and thus achieving a more perfect layering effect.
One of the main reasons is that it is easier to drink coffee and milk together when you drink it, rather than the embarrassing situation of drinking a large sip of concentrated milk and leaving the milk at the bottom of the cup. What if you want a more pronounced layering effect?
After we learned that the main reason why milk can be stratified with concentrate is because of the difference in density between them. When we want a more perfect stratification effect, then we can try to increase the concentration of the milk, further widening the density difference between it and the concentration, so as to produce a more absolute stratification effect. Then, using Ice Bock is the best choice.
Using the concentration meter to measure the milk concentration separately, it can be seen that the ice bock far exceeds that of ordinary milk).
Ice Bock production method) Qianjie wrote this article before the main talk is how to make a higher concentration, more flavorful milk at home, with it to make a dirty taste more amazing, when you have nothing to do, then pick a bottle of lucky milk and throw it in the refrigerator, the next day waiting for the end of the drip to make a rich, silky, sweet ** dirty
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