How to Make a Sourdough Starter from Scratch (a Beginner's Day-by-Day)

A sourdough starter is just flour and water left alone long enough to catch wild yeast out of the air. That's it. No special equipment, no sourdough gene you were either born with or not. If you have flour, water, a jar, and about a week, you can make one. I did, with absolutely no idea what I was doing, and mine is still going.

Here's the whole thing, one day at a time, in plain language.

What you need

• A clean jar (a mason jar is perfect)
• Flour. Whole wheat or rye to start, because the wild yeast likes it better, then plain all-purpose after that
• Water, ideally not straight from a heavily chlorinated tap. Filtered or left-out-overnight is fine
• A kitchen scale if you have one. Cups work too, and I'll give you both

Day 1: mix it and walk away

Put 60 grams of whole wheat flour (about ½ cup) and 60 grams of water (¼ cup) in the jar. Stir until there's no dry flour left. It'll look like thick paste. Put the lid on loosely, or a cloth and a rubber band, and set it somewhere warm-ish, around 75°F. On top of the fridge is a classic spot. Now leave it alone for 24 hours. Nothing to do, nothing to watch.

Days 2–3: the first bubbles (and the first smell)

You might see a few bubbles. You might not. Either is normal. Give it a stir. Now start feeding: keep about 2 tablespoons of what's in the jar, throw the rest out or save it, and stir in another 60 grams flour and 60 grams water. Around now it may smell sharp, almost like nail polish remover. Don't panic. That's not rot, it's hungry, and feeding is the answer.

Days 4–5: it starts to look alive

This is where most people either quit or fall in love. The starter should be bubbling more, rising a bit after you feed it, and smelling less like acetone and more like sour yogurt or beer. Keep the daily rhythm: discard down to a couple tablespoons, feed with equal flour and water, wait. Same time each day if you can. It likes routine as much as you do.

Days 6–7: the rubber band test

To know when it's actually ready to bake with, do this. Right after you feed it, stretch a rubber band around the jar at the level of the starter. Then watch. When it reliably doubles in height within about 4 to 6 hours, dome up gently, then hold, it's alive and strong enough to raise bread. If it's sluggish, it just needs a few more days of feeding. Warmth and patience fix almost everything at this stage.

What to do when yours doesn't cooperate

Mine did not read the instructions, and yours might not either. The two things that go wrong:

• Nothing's happening by day 5. Almost always too cold. Move it somewhere warmer and feed it twice a day for a few days.
• It rose fast, then went flat and smelly. It ate everything and got hungry. That's a good sign. Just feed it sooner next time.

The one thing that is a real emergency is pink or orange streaks, or fuzzy mold. That's the rare case where you throw it out and start over. Sharp smells, grey liquid on top, sluggishness, none of those mean it's dead. They mean it wants feeding.

You're allowed to name it

Mine was Rylie. People name their starters because you end up talking to it, and because a thing with a name is a thing you keep alive. It's a low bar for a friendship and a very forgiving one. Your starter is much harder to kill than you think.

The truth about starters is that the hardest part is trusting that nothing-looks-like-it's-happening is exactly what should be happening. Give it warmth, feed it on a schedule, and wait. In a week you'll have a living thing that turns flour and water into bread. Bake it anyway, even the first ugly loaf. Especially that one.

Want the full 30-day version on a printable calendar, with a feeding chart and a what-am-I-looking-at photo guide? That's Starter School, our beginner starter guide.