What Causes Espresso Extraction to Be Sometimes Fast and Sometimes Slow? What's the Difference Between Tamping and Not Tamping? What Are the Consequences of an Overheated Grinder?

Sometimes fast, sometimes slow, sometimes delicious, sometimes not. Yes, FrontStreet Coffee is talking about the unstable state that can occasionally occur with espresso when making consecutive cups. Not only does the extraction time fluctuate between fast and slow, but even the taste of the coffee produced is unpredictable.

This is a problem that troubles many people. When the grind size and coffee dose are identical, why is there such a significant difference in extraction? If you're experiencing this situation, it's likely caused by one of these three reasons! Let FrontStreet Coffee explain step by step~

1. No Pressure Applied to the Bean Hopper

"Pressure applied" and "no pressure applied" are two terms we often hear! Pressure applied means exerting significant pressure on the coffee beans about to be ground. This pressure can come from the accumulated weight of a large quantity of coffee beans or from other materials. No pressure applied means only pouring a small amount of beans, just enough for one or a few extractions, where the coffee beans being ground are not subjected to any pressure. (For reference only: left side shows pressure applied, right side shows no pressure applied)

Since the difference between pressure applied and no pressure applied is not our main topic, FrontStreet Coffee will briefly explain here: When grinding with pressure applied, the coffee beans won't jump randomly due to the pressure when squeezed by the burrs, resulting in more uniform particles. When grinding without pressure applied, the coffee beans, lacking pressure, tend to be ejected when squeezed by the burrs, then fall back to be ground again, repeating this process. A single coffee bean might be ground multiple times, resulting in less uniform and coarser particles. Since the particles ground without pressure applied are not uniform and differ with each grinder, this poses a significant variation for pressurized extraction methods that are extremely sensitive to consistency! Naturally, the extraction state and espresso taste will be affected accordingly.

Therefore, if we need to extract a larger quantity of cups, it's best to choose pressure applied! Applying pressure to the coffee beans ensures more uniform particles, thus stabilizing the extraction state. The material used for pressure applied doesn't necessarily have to be coffee beans; it can be other weighted objects, as long as they are properly sealed~

2. Burr Heating

When you continuously make too many cups and the burrs work frequently, they will generate heat. Hot burrs make the coffee beans they contact more brittle, in other words, easier to grind. However, this also makes the ground coffee particles coarser, thus changing the flow rate.

In addition, hot burrs accelerate the loss of flavor compounds in the coffee grounds because their higher temperature naturally speeds up oxidation, which is the enemy of flavor. Therefore, for friends extracting at home, to ensure extraction stability, we can choose to appropriately slow down the extraction pace. For friends in coffee shops, it's best to make corresponding adjustments to extraction parameters. (But we don't recommend changing the grind size; adjusting the coffee dose will suffice)

3. Coffee Machine Boiler Issues

Another reason could be problems with the coffee machine. Many coffee machines chosen by friends don't support simultaneously frothing milk and extracting espresso! Even if they can, they cause the pressure/water temperature provided by the coffee machine during extraction to be extremely unstable, ultimately leading to significant deviations in extraction time and coffee taste.

The solution for this situation is quite straightforward: follow the sequence step by step! Extract espresso first, then froth milk! This way, the boiler won't be under too much burden during extraction, ensuring stable performance~

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473