The Role of Secondary Distribution Screens: Are Bomber's Screens Effective? Solving Wet, Poorly Formed Coffee Pucks During Extraction

As we all know, the coffee world occasionally produces some "physical hacks" that assist us in making better high-quality coffee in different aspects. For example, in the pour-over coffee field, there are paper filters and shower drippers. In the espresso field, there are distribution tools, bottomless portafilters, and so on.

Today, FrontStreet Coffee wants to share a trending auxiliary tool from a while ago! It's a small piece of metal that claims to make coffee extraction simpler - it's the secondary distribution screen!

Many of you might find this name unfamiliar, but that's okay! FrontStreet Coffee will first introduce what a distribution screen is, and then it won't be difficult for us to get to know the secondary distribution screen!

What is a Distribution Screen?

We can see a mesh-like area inside the espresso machine's group head. That area is the coffee machine's water outlet, which we often call the distribution screen (it can be removed for cleaning).

The distribution screen is the closest part to the coffee puck during espresso extraction. The hot water we use to extract the puck is drawn from the coffee machine's water tank, then transported through pipes to the distribution screen, which then "splits" the water to evenly sprinkle over the puck for extraction. Therefore, we can understand that the main function of the distribution screen is to disperse hot water and apply it evenly to the puck!

People discovered that some coffee machines cannot achieve even water distribution, or often friends experience frequent channeling due to uneven distribution, causing extraction variations! Thus, the secondary distribution screen was born! Simply install it on the puck, and it can redistribute the hot water dripping from the group head's distribution screen, ensuring the puck receives water evenly, making extraction more uniform, and greatly increasing the probability of making delicious espresso.

In addition, it's rumored online that it can also make the knocked-out puck more complete - a blessing for those with OCD! So is this really the case? Let FrontStreet Coffee conduct an experiment to compare and see if the secondary distribution screen truly has these effects!

Extraction Experiment

For this experiment, FrontStreet Coffee will continue using the Warm Sun Blend. The extraction parameters remain identical - using 20g of coffee to extract 40ml of coffee liquid, with the only difference being that one is regular extraction, while the other uses the secondary distribution screen for extraction.

Excellent! Because the distribution was very even, neither extraction experienced channeling during the process. The regular extraction took 30 seconds, while the espresso extraction with the secondary distribution screen took 33 seconds. From this, we can see that the extraction time increased somewhat when using the secondary distribution screen.

After tasting, FrontStreet Coffee discovered a very obvious difference between the two - the espresso with the secondary distribution screen had明显的过萃味道! The concentration meter helped verify this observation - its extraction rate was a full percentage point higher than the regular extracted espresso.

Actually, FrontStreet Coffee had already predicted this result before drinking! Because when locking the portafilter, the one with the secondary distribution screen transmitted obvious resistance. In other words, even though this secondary distribution screen is as thin as paper, it still takes up some space. Therefore, its existence is equivalent to us increasing the amount of coffee in the puck. The increased amount of coffee caused the overall resistance of the puck to increase accordingly, and the coffee machine needed to apply more pressure to extract the espresso. This led to the coffee puck being subjected to higher extraction efficiency, prolonged extraction time, increased pressure, ultimately resulting in the extraction of bitter flavors that shouldn't have been extracted.

So FrontStreet Coffee regrouped and reduced the coffee amount by 0.4g. As expected, the coffee extraction time returned to normal, and the extraction rate was also corrected. Of course, the liquid weight was relatively reduced as well. Then, from the evenness of the color distribution on the puck, we can tell that the hot water was indeed distributed evenly, and the coffee extraction was indeed more uniform compared to not having the secondary distribution screen installed. Most importantly, because this secondary distribution screen first bore the impact of pressurized hot water during the extraction process, and then applied even pressure to the puck, the puck surface wouldn't be scattered by concentrated hot water and was further stabilized. When knocked out, it was indeed very complete - truly a blessing for OCD sufferers!

The distribution screen on the group head also didn't contact the puck due to the presence of the secondary distribution screen, and remained relatively clean after pressure release. (But it still needs to be washed!)

Conclusion

In summary, the secondary distribution screen does indeed achieve the rumored effects: making extraction more even and producing perfect pucks. However, we need to understand that if we decide to use the secondary distribution screen for extraction, then when adjusting espresso, we need to include the secondary distribution screen in the debugging process. After extraction is complete, we also need to risk burning our hands to retrieve the secondary distribution screen from the puck, and then perform additional cleaning. The tool is indeed useful, but the operational process it brings is also relatively more cumbersome. You can't have your cake and eat it too. If you want to make a more refined espresso, then adding the secondary distribution screen is indeed a good choice. But if friends are like FrontStreet Coffee, wanting to simply make a delicious espresso, then it's better to focus on tamping well and adjusting the espresso properly~

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473