Day One: Flour, Water, and a Wide-Mouth Jar
Today isn't about baking — it's about 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 one job is to feed it consistently until it's strong enough to lift a loaf of bread. Here's the setup.
What you need on the counter
- A wide-mouth quart jar. Mine's just a mason jar from the canning box. Wide mouth matters because you'll be reaching in with a spatula and 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 flour choice another day; for day one, whatever bread flour you've got is fine.
- 100 grams water, room temperature — not straight from the fridge.
- A scale. You already know where I stand on cups versus grams, so I'll say it once, plainly: weigh it. A starter you eyeball with a measuring cup is one you can't troubleshoot later, because you won't know what you actually did.
- A rubber band or a piece of tape to mark the level on the jar.
That's the whole list. 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, or inside the oven with just the light on (not the oven itself). Our house runs cool in winter, so I use the oven-light trick more often than not.
Then 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 — I mean that specifically, not a general "ew." Pink means throw the whole thing out, wash the jar hard, and start over. 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 once converted a bread recipe to baker's percentages 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, straight-faced, whether the deck was made of dough now. I didn't have a good answer. 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 forgotten, 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, a 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.