Day One: Flour, Water, and a Wide-Mouth Jar
Okay. Today we're not baking anything. Today we're growing something.
A sourdough starter is just flour and water left out until wild yeast and bacteria move in and start eating. Nobody's selling you the yeast. It's already on the flour, in the air in your kitchen, on your hands. Your job is to feed it consistently until it's strong enough to lift a loaf of bread. That's the whole project.
What you need on the counter
- A wide-mouth quart jar. Mine's just a mason jar I had in the canning box. Wide mouth matters because you'll be reaching in with a spatula and you don't want to fight the opening.
- 100 grams King Arthur bread flour, or a whole wheat/bread flour mix if you have it. We'll talk more about flour choice another day, but for day one, don't overthink it. Whatever bread flour you've got is fine.
- 100 grams water, room temperature. Not straight from the fridge.
- A scale. If you sat through my rant on cups versus grams, you already know where I stand. I'm not going to repeat the whole speech, but I will say this again plainly: weigh it. A starter you eyeball with a measuring cup is a starter you can't troubleshoot later, because you won't know what you actually did.
- A rubber band or a piece of tape, something to mark the level on the jar.
That's it. No special container, no starter kit, no discard tool. Buy the flour first.
The actual steps
- Weigh 100 grams flour into the jar.
- Weigh 100 grams water into the jar, right on top.
- Stir it together until there's no dry flour left. It'll look like thick pancake batter. Lumpy is fine.
- Scrape down the sides so nothing's crusting on the glass.
- Put the rubber band right at the top of the mixture. This is your marker. Tomorrow and the day after, you're watching to see if it climbs above that line.
- Cover loosely. A coffee filter with a rubber band, or the jar lid set on top without sealing it. You want air moving, not a vacuum-sealed jar. This isn't a canning project.
- Set it somewhere around 75 to 80 degrees if you can manage it. Top of the fridge, near a sunny window, inside the oven with just the light on (not the oven itself). Our house runs a little cool in winter, so I use the oven-light trick more often than not.
Then you leave it alone for 24 hours. That's the hard part, and it's the whole lesson today. Nothing to check, nothing to feed, nothing to stir. Just wait.
What you'll actually see, or won't
On day one, probably nothing. Maybe a few small bubbles if you're lucky and your kitchen's warm. Don't panic if it looks exactly like when you mixed it. That's normal. This isn't bread yet, it's not even really a starter yet. It's flour and water auditioning for the job.
If you see pink or orange anywhere in there, that's mold, and I mean that specifically, not a general "ew." Pink means throw the whole thing out, wash the jar hard, and start over. I'll tell you flat out I learned that one from a starter I almost cried over. Don't get attached this early. It's just flour and water, you can mix another jar in five minutes.
A word on measuring, since we're here
I'll admit I take this ratio thing further than most people would find normal. I converted a bread recipe to baker's percentages once on the back of a lumber takeoff sheet I had in the truck, because it was the paper closest to hand and I wanted the numbers down before I lost the thought. Richard found it weeks later going through the console and asked me straight-faced if the deck was made of dough now. I didn't have a good answer for him. But that's genuinely how my brain wants to hold onto this stuff, in ratios, on whatever scrap of paper is nearby. If you're a numbers person too, don't fight it. Write it down.
A real caution, not a lawyer one
If your kitchen runs warm, don't tuck this jar somewhere completely sealed and forgot-about, like a cupboard with the door shut tight. Gas builds up as it ferments and a totally sealed jar can actually push a lid off with some force. Loose cover, room with airflow, and you're fine.
Before next time
Don't touch it, don't feed it, don't peek every hour hoping for bubbles. Just get the jar set up in a warm spot and let it sit the full 24 hours. We'll check in on it and do the first feeding together next lesson.