A bottomless portafilter is useful for seeing where coffee leaves the basket. It is not a sweetness meter. A tidy stream can still produce a disappointing espresso, and an untidy start does not tell you exactly what happened inside the puck.
What spraying is useful for
Sideways jets or repeated spraying make it worth checking preparation. Start with actual dose, even distribution and a level tamp. Inspect the basket for damage or blocked holes. If you immediately grind finer, you may hide one symptom while making flow less consistent.
Position the cup and scale so you can see without leaning beneath the group. Espresso and metal are hot; do not touch the basket during brewing. Keep phones and electrical equipment away from spray. Stop a shot if the setup becomes unsafe.
One stream is an observation, not a certificate
Streams may join as coffee covers the underside of the basket. The joining point depends on the basket and flow, not only on your skill. Do not chase a central stream by repeatedly changing the tamp angle. A level puck is the goal, even if the basket's underside directs the drink slightly off centre.
Freshness, roast and the recipe influence how the drink looks. Crema colour alone cannot establish whether a shot is under-extracted or over-extracted. You need the taste, dose and yield to make the observation useful.
Record a controlled comparison
Use a simple log: "18 g dose, 36 g out, same setting; small jet on right; sharp finish." For the next shot, improve distribution but leave dose, grind and yield unchanged. If the spraying stops and the cup improves, you have a reason to keep that preparation change. If only the appearance improves, do not claim that the flavour problem is solved.
Use the same cup position and camera angle if you record video. A five-second clip of the most attractive part of extraction can conceal the messy beginning. Review the whole shot, including whether the flow suddenly accelerates near the end.
When to stop looking underneath
If several shots run similarly but taste wrong, move back to the recipe. Compare a different beverage weight or make a modest grind adjustment. The dialing-in guide separates those changes from preparation.
You do not need a bottomless portafilter to make good espresso. A scale and a consistent routine give you more actionable information than an attractive extraction video without weights. Use the open basket when you need to diagnose a visible problem, then put your attention back on the cup.
