The jar on your counter, demystified.

How to know it's ready to bake with

Not by the clock, and not by the smell alone. A starter is ready when it has reliably doubled after a feed, looks domed and bubbly rather than sunken, and does it on roughly the same schedule two or three days in a row.

The float test (a spoonful dropped in water) is a rough signal, not proof. Predictability is the real signal.

Normal things that scare people

• A layer of dark liquid on top.That's alcohol. It means the starter is hungry, not dead. Pour it off or stir it in and feed.
• It smells sharp, like acetone or nail polish. Also hunger. More frequent feeding, or a cooler spot, calms it down.
• It rose beautifully last week and now it's sluggish. Kitchen temperature changed. Starters are much slower in a cold room.
• Grey or discoloured on the surface. Usually oxidation. Scrape it off and carry on.

Things that actually mean start over

• Fuzzy mouldin pink, orange, green or black, anywhere in the jar. Throw the whole thing out, jar included if it's plastic.
• Streaks of pink or orange through the starter itself. Not salvageable.

Anything short of visible mould is almost always fixable with a few days of regular feeding.

Keeping it alive when you're not baking

A starter in the fridge slows right down and can go a week or more between feeds. Take it out, feed it, and give it a day or two at room temperature before you plan to bake with it. It won't perform straight out of the cold.

If you bake most weeks, a jar on the counter fed on a routine is simpler. If you bake occasionally, the fridge saves you a lot of flour.

Starter journals

The plan for this section is a running log per baker: what you fed it, what the kitchen temperature was, how high it rose, and how the resulting loaf turned out. Over a few weeks that log tells you more about your own starter than any general advice can.