Why Is the Coffee Crema Less Rich When Using a Bottomless Portafilter?

Many coffee enthusiasts switch to a bottomless portafilter (naked portafilter) to achieve a more professional extraction and visual experience. However, after using a bottomless portafilter, many people notice a significant reduction in coffee crema and even experience unstable extraction. This phenomenon is influenced by multiple factors, including basket design, technique, and equipment compatibility. This article will analyze the reasons behind the reduced crema and provide targeted solutions.

1. Core Principles

1. Differences in Basket Types

• Pressurized Basket: Equipped with a built-in pressure valve to force extraction, it can produce a large amount of loose foam (often referred to as "fake crema") even with stale or coarsely ground coffee.

• Non-Pressurized Basket (standard for bottomless portafilters): Relies on coffee bean quality and technique. The crema is naturally emulsified from coffee lipids, resulting in a golden-brown color and stronger persistence.

2. Exposure During Extraction

The bottomless portafilter exposes the coffee puck directly. Improper techniques (e.g., insufficient coffee dose, uneven tamping) can lead to channeling, causing thin crema or splattering during extraction.

Summary: The non-pressurized basket in a bottomless portafilter relies on coffee bean quality and technique, while the pressurized basket uses a built-in valve to create "fake crema." Therefore, reduced crema when using a bottomless portafilter often indicates issues with technique or equipment compatibility.

2. Four Major Causes of Insufficient Crema and Solutions

1. Coffee Dose and Basket Mismatch

• Issue: Non-pressurized baskets have a larger capacity. Using an old dose (e.g., 16g) can result in a thin puck and fast water flow.

• Solution:

  1. Follow the basket's recommended dose (usually 18-20g for double baskets);

  2. After dosing, gently tap the portafilter to distribute the grounds evenly, ensuring the coffee bed is 1-2mm below the rim.

• Tip: Use a scale to measure the dose accurately and ensure consistency.

2. Grind Size Too Coarse

• Issue: Non-pressurized baskets require a finer grind to increase resistance. A coarse grind can lead to fast flow (extraction time less than 25 seconds for 60ml).

• Solution:

  1. Adjust the grind size to resemble granulated sugar (with slight resistance when pinched);

  2. Aim for an extraction time of 25-30 seconds for 60ml (double shot).

• Tip: Make small adjustments to the grind size to avoid overcorrecting and affecting extraction.

3. Poor Portafilter Seal

• Issue: Mismatched portafilter lugs or worn gaskets can cause pressure leaks (pressure below 9Bar).

• Solution:

  1. Tighten the portafilter to a vertical angle (around 30°);

  2. Check the group head gasket and replace it if worn.

• Tip: Regularly inspect the gasket and replace it every 3-6 months to ensure a proper seal.

4. Stale Coffee Beans

• Issue: Beans roasted more than 3 weeks ago or stored improperly (not airtight or light-protected) may lack sufficient carbon dioxide.

• Solution:

  1. Use beans roasted within the last 7-21 days;

  2. Choose medium to dark roast beans (richer in lipids).

• Tip: Purchase freshly roasted beans and store them in an airtight, light-proof container.

3. Quick Self-Check Steps

1. Test with the Original Portafilter:
   If the crema returns, the issue may lie with the bottomless portafilter or technique. Recheck the installation and usage of the bottomless portafilter.

2. Check the Coffee Dose:
   Use a scale to confirm the dose is 18-20g (for double baskets).

3. Time the Extraction:

   • If the flow is too fast (extraction time less than 25 seconds), adjust to a finer grind;

   • If the flow is too slow (extraction time over 30 seconds), adjust to a coarser grind.

4. Empty Portafilter Test:
   Run the machine without coffee. The water flow should be even and steady; if it splatters, the seal may be faulty. Check the group head gasket and portafilter seal, and replace if necessary.

4. Conclusion

The reduction in crema when using a bottomless portafilter is due to the absence of the "artificial foam" created by pressurized baskets, shifting the focus to real extraction techniques. Insufficient coffee dose, coarse grind, poor portafilter seal, or stale beans can all lead to thin crema. By adjusting the dose to 18-20g, using a finer grind (25-30 seconds for 60ml), ensuring a proper seal, and using fresh beans, you can achieve a rich, golden-brown crema with a cleaner and more distinct flavor profile.

Additional Tips:

• Balancing Visuals and Flavor: While a bottomless portafilter may reduce crema, it provides a clear view of the extraction process, helping identify issues like channeling. Less crema doesn’t necessarily mean worse flavor; it can result in a cleaner and more nuanced cup.

• Practice and Adjustments: Using a bottomless portafilter requires experience and patience. Experiment with different doses, grind sizes, and tamping pressures to find the optimal parameters for your equipment and beans.