Why Does the Coffee Puck Stick to the Group Head? Does a Puck Stuck to the Shower Screen Affect Espresso?

Why Coffee Puck Sticks to the Group Head

A few days ago, FrontStreet Coffee shared an article about "Reasons for Water Accumulation in Coffee Portafilter," and some friends asked, "What causes the coffee puck to stick to the group head after extraction?" Therefore, FrontStreet Coffee will discuss why this situation occurs.

Too Much Coffee Grounds

This is the easiest problem to identify, yet it has the minimal impact. FrontStreet Coffee has mentioned that under ideal conditions, there should be a slight gap between the surface of the coffee puck and the shower screen in the group head. When extraction begins and moistens the coffee puck, it will expand slightly.

If there's too much coffee, the surface of the puck will directly contact the shower screen after locking the portafilter. When extraction ends, the group head will suck back excess water, making it easy for the puck to stick to the group head.

However, excessive coffee grounds don't always cause sticking. While coffee puck sticking to the group head is often related to excessive grounds, the probability of this phenomenon being directly caused by it isn't very high – it might occur about once in ten attempts. The fresher the coffee beans, the more likely the puck will stick to the group head due to excessive grounds.

Delaying Portafilter Removal After Extraction

This situation most commonly causes coffee pucks to stick to the group head. After extraction ends, if you don't remove the portafilter immediately, the puck will stick to the shower screen as moisture dries, gradually adhering to it.

The combination of excessive grounds and delayed portafilter removal after extraction makes it very likely for the puck to stick to the group head. As long as the extraction parameters are within reasonable ranges, an occasional puck sticking to the group head won't affect the flavor expression of the espresso. If this happens frequently, it's better to reduce the amount of grounds and adjust the parameters.

Heat Effect on Coffee Grounds

Just as FrontStreet Coffee uses slightly more grounds than the basket's capacity specification, if you lock the portafilter onto the group head and remove it after 10 seconds, the high-temperature, moist shower screen will absorb some of the coffee grounds.

Therefore, when the portafilter is locked and the puck contacts the shower screen, if extraction is delayed, the puck's surface will be "scorched" by the high temperature, resulting in burnt bitterness. However, if extraction starts immediately after locking the portafilter, no flavor abnormalities will occur.

Loosened Coffee Puck

Another phenomenon occurs when the coffee puck gets accidentally bumped between distribution and tamping, before locking onto the group head, causing a gap between the puck and the basket. Similarly, when there's more coffee, it's more likely to stick to the shower screen. This situation will cause channeling due to the loose connection between the puck and basket, thereby affecting the espresso's performance.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473