Blue Bottle Coffee · Night Light Decaf

Shot 2 on Night Light Decaf at grind 42 — 23s, 18.2g adjusted dose, 39.4g yield, balance 5, slightly bitter. The right spout dropped briefly mid-shot before recovering, and flow ran faster on the left throughout. Time improved from shot 1 (28s → 23s) but is now on the fast side, and the bitter-then-sour flavor sequence you're describing is a classic sign of uneven extraction — over on one side, under on the other — consistent with that asymmetric flow.

Time is Fast at 23s (industry under-extracted territory, below the 25s floor). Ratio is Normal at 2.16. The 9g lag is your Bambino working as expected — normal. You targeted a 25–30s pull and landed short by about 2 seconds on the low end. The balance 5 (slightly bitter) combined with the sour-after-bitter taste sequence is the real signal here: if extraction were even and simply fast, you'd expect pure sourness. The bitter-first flavor that pivots to sour suggests the right side under-extracted while the left over-extracted — the flow imbalance you saw isn't cosmetic.

Night Light Decaf is a Swiss Water medium roast — it degasses fast and extracts easily. At 15 days since roast it's squarely in peak window, so freshness isn't a factor. The crème brûlée and key lime notes in the profile could explain some of the complexity you noticed, but the bitter-pivot-to-sour sequence is more consistent with uneven extraction than bean character. The bag's tasting notes suggest a clean, cocoa-forward profile — you should be getting sweetness and roundness here, not a tug-of-war between bitter and sour.

Your instinct to go finer after shot 1 was right — but the right-side flow imbalance is doing as much damage as the grind setting. Once the puck prep is evening out, the dial-in will move faster.