How to Make a Sourdough Starter From Scratch — A Realistic 14-Day Guide

A sourdough starter is nothing more than flour and water left to attract the wild yeast and bacteria already present in the flour and the air around you. No purchase required, no special equipment, no secret ingredient. Just time and consistency.

We should be upfront: we sell established starters, so we have an obvious interest here. This guide is written honestly anyway — including the parts that are genuinely difficult — because a baker who understands what's happening in the jar bakes better bread regardless of where the culture came from.

What You Need

• Wholemeal rye or wholemeal wheat flour for the first few days. Wholegrain flours carry far more wild yeast and bacteria than white flour, which gets the culture started much faster. Rye is the fastest.
• Unbleached white bakers flour for later feeds.
• Filtered water, or tap water left out for an hour so the chlorine dissipates.
• Digital scales accurate to 1g. Not optional — cups won't get you there.
• A tall narrow jar, 400–600ml. A wide jar makes a healthy rise invisible and is a common reason people conclude it isn't working. Our starter jar is sized for this.
• A warm spot, ideally 24–26°C.

Day 1 — Mix

Combine 50g wholemeal rye or wheat flour with 50g water. Stir to a thick paste, scrape down the sides, and cover loosely. Mark the level with a rubber band.

Leave it 24 hours somewhere warm. Nothing much will happen, and that's correct.

Days 2–3 — The False Rise

You'll probably see bubbles and a noticeable rise, and it may smell unpleasant — sharp, cheesy, sometimes a bit like vomit.

This is not your sourdough culture. It's Leuconostoc and other opportunistic bacteria having a brief population boom. They die off as the mixture becomes more acidic. Knowing this in advance is what stops you being disappointed on day four.

Feed once daily: discard all but 50g, then add 50g flour and 50g water.

Day 4 — Everything Stops

The bubbles vanish. The rise disappears. The jar looks dead.

This is the single biggest reason people abandon a from-scratch starter, usually one or two days before it would have worked. The early bacteria have died off and the wild yeast hasn't yet built up enough population to take over. The jar is quiet because it's between tenants.

Keep feeding. Nothing is wrong.

Days 5–7 — Real Activity Begins

Small, even bubbles start appearing through the mixture rather than just on top. The smell changes from unpleasant to sour, yeasty, and faintly like yoghurt or beer. You may see a modest rise.

Switch to feeding twice daily now, roughly 12 hours apart, and start blending in white bakers flour — half wholemeal, half white — as you move toward your final maintenance routine.

Days 8–14 — Building Strength

Move to a 1:2:2 ratio: 20g starter, 40g flour, 40g water, twice a day. Bigger feeds dilute accumulated acid and give the yeast more to work with.

Watch for the rise-and-fall cycle becoming predictable. That predictability, not the height of the rise, is the real sign of a mature culture.

How to Know It's Ready to Bake With

Your starter is ready when it does all of these consistently, not just once:

• Doubles reliably within four to eight hours of feeding at room temperature
• Domes at peak, then falls predictably
• Smells clean and tangy — never like nail polish remover or anything rotten
• Passes the float test at peak
• Behaves the same way several days in a row

Most from-scratch starters reach this at 10–14 days. Some take three weeks. Baking too early is the most common cause of a dense first loaf — our guide on reading your starter covers the signs in detail.

When It Goes Wrong

• No activity after 10 days — almost always temperature. Below 20°C progress is glacial. Find somewhere warmer before changing anything else.
• Pink, orange, or fuzzy growth — genuine contamination. Discard, sterilise the jar, start again.
• Smells like acetone — hungry, not dead. Feed more often, or at a bigger ratio.
• Rises and falls before you check — that's success, not failure. Mark the jar and check more frequently.

More detail in why isn't my starter rising.

Should You Do This at All?

Here's the honest version.

Making your own is free, genuinely satisfying, and teaches you more about fermentation than any amount of reading. If the process interests you as much as the bread does, do it.

The trade-offs are real though. It takes 10–14 days minimum before you can bake. A meaningful share of attempts fail — usually abandoned during the day-four slump. And in the early weeks the culture is unpredictable, so your first loaves are often disappointing in ways that are hard to diagnose when you can't yet tell a weak starter from a bad technique.

An established culture skips all of that. Ours are wheat and rye, both maintained continuously for years, ready to bake with 24–48 hours after arrival, and replaced free if they don't activate.

Neither path is wrong. We've written a fuller comparison in scratch or buy.

Once It's Alive

Learn the maintenance routine in our starter care guide, then bake your first loaf with the classic sourdough recipe. And once it's healthy, dry a backup — two weeks of work deserves insurance.