Why doesn't my loaf get an ear, even when I score deep?

An ear isn't built by depth alone — it's built by the angle of the blade. Hold the lame at roughly 30° to the surface and cut a single decisive slash, so a flap of skin lifts as the dough pushes outward. A perpendicular 90° cut just opens; only an angled cut peels back. If you're already cutting at 30° and still no ear, the dough is over-proofed: there's no spring left to lift the flap.

How much steam, and for how long?

Plenty for the first 10–20 minutes, then dry for the rest of the bake. In a Dutch oven, the dough's own moisture is enough — keep the lid on for 20 minutes. With a stone or steel, throw 100–150 ml of boiling water into a hot tray on the bottom rack at the moment of loading, and vent the oven at 20 minutes. Past that point, steam keeps the crust soft and stops it from colouring — exactly what you don't want.

What internal temperature means a sourdough is actually done?

96–99°C (205–210°F) at the centre, measured with a probe thermometer. Below 95°C the crumb is still gummy in the middle, even if the crust looks dark. Above 99°C you're starting to dry the crumb out. If you bake without a probe, tap the bottom — a deep, hollow knock is the proxy, but the probe is honest and the bottom-tap takes a hundred bakes to read reliably.

Why is my crust pale on top but dark on the bottom?

Almost always uneven heat distribution. Many home ovens load most of their thermal mass into the floor element; the top element kicks in late or weakly. Two fixes: bake on the middle rack (not the bottom), and preheat the oven for at least 45 minutes with the Dutch oven or stone inside. The vessel needs to be saturated with heat, not just the air. If the top is still pale at minute 30, switch to convection or move up one rack.

Should I score with a razor blade or a serrated knife?

A double-edged razor (lame) on a curved or straight handle, every time. Serrated knives drag and tear the skin instead of slicing it; the cut closes back up before the bake. A razor is sharp enough to part the surface in one motion, which is what lets the cut hold its shape during oven spring. Wet the blade or oil it lightly if it's catching — that means the blade is dull, not the technique.

Scoring and Baking: How a Knife and Steam Build the Ear