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Channeling happens when water takes easier paths through an espresso puck instead of moving evenly through the bed. Some areas can remain underextracted while others contribute a harsh finish. The result may taste both sour and dry, so simply making the grind finer can make diagnosis harder.

Look for a pattern, not one dramatic clue

Spraying from a bottomless portafilter, an unexpectedly fast finish after a slow start, or large shot-to-shot differences can suggest uneven flow. None is a complete diagnosis on its own.

Holes in a spent puck are especially easy to overinterpret. Pressure release and puck removal can change its appearance after brewing. A wet puck also does not automatically mean the extraction failed.

Compare taste, dose, yield, time, and visible behavior together. You do not need a bottomless portafilter to improve consistency; it is an observation tool, not a requirement for good coffee.

Check basket fit and condition

Use a clean, dry basket and a dose within its practical working range. Too much coffee can leave insufficient headspace, while too little can create a bed that is difficult to prepare consistently.

Inspect holes for blockage and the basket for damage. Clean coffee oils with an appropriate method, rinse well, and dry before dosing. Make sure the shower screen and gasket area are maintained according to the machine's instructions.

Do not force the portafilter into place when the puck is overfilled. Reduce the dose or use the correct basket instead of treating the shower screen as a compression tool.

Distribute before tamping

Grind so the basket does not end up with a tall mound on one side and an empty edge on the other. A dosing funnel can reduce spills while you distribute.

If the grinder produces clumps, a suitable thin-needle distribution tool can help separate them through the depth of the bed. Finish with a reasonably level surface. Flattening only the top may hide uneven density underneath.

Tamp level on a stable support. Apply consistent pressure, then leave the puck alone. Hard knocks after tamping can disturb the edge and create a separation you did not intend.

Do not use excessive resistance as a cure

An overly fine grind can choke the puck and encourage water to find weak paths. If a finer adjustment makes the shot less predictable or produces more spraying, return toward the previous setting.

Keep the target beverage weight fixed while testing a modest grind change. Otherwise a slower shot stopped at a different yield mixes two effects together.

Follow the grinder's adjustment instructions and account for retained coffee when changing settings. A shot containing a mixture of old and new grind sizes may not represent the new setting well.

Use a small consistency test

Prepare several shots with the same dose, yield target, and warmup routine over ordinary use. Record whether the timing range narrows and whether the flavor becomes more coherent.

If the improvement follows better distribution, keep that step. If the problem remains, inspect machine water delivery or seek model-specific guidance rather than adding accessories blindly.

A puck screen or specialized basket can change the workflow and available headspace. Add one only for a defined reason and evaluate it separately. Preventing channeling is mainly about a suitable bed, even preparation, and controlled resistance, not building the most elaborate puck-prep sequence.