Specialty Coffee Bar Kit

Flat burrs produce a more uniform grind (more clarity and sweetness in the cup) but are pricier and retain more coffee. Conical is cheaper and lower retention. For pour-over at the top end, flat burrs edge it out; for most people, a good conical is plenty. Upgrade the burrs when you have upgraded the beans first.

Coffee peaks 3 to 14 days after roasting and goes stale (oxidized, flat) within a month. Grocery-store beans are months old by the time you buy them. A local roaster or a subscription ships beans within days of roast, and the cup is dramatically more aromatic — the single biggest quality factor.

Airtight, opaque, at room temperature — not in the fridge or freezer (moisture and odor absorption). A canister with a one-way valve (lets CO2 out, no oxygen in) is ideal. Grind on demand; ground coffee stales in an hour. Buy a week's worth at a time, not a month's.

Extraction is how much of the coffee dissolves into the water. Too little (under-extracted) is sour and weak; too much (over-extracted) is bitter and harsh. Dial in by adjusting the grind: finer for more extraction (if sour), coarser for less (if bitter), keeping the ratio and time constant. The sour/bitter signal is the compass.