Sourdough Starter from Scratch: A Day-by-Day 7-Day Guide

A jar of flour and water can sit there looking like nothing for two days, then climb the glass on the third morning like something alive. That early drama fades fast. Day four is usually flat and discouraging, and by day seven you have a starter that doubles on schedule and smells like yogurt and beer. The plan below uses one feeding ratio, one time of day, and a short list of signs that tell you when it is genuinely ready to raise a loaf.

Before Day One: Four Things to Get Right

You need four things, and none of them are expensive.

• Flour. Whole wheat or rye for the first week, because the bran carries more of the microbes you want. Unbleached all-purpose works too; it just tends to take a day or two longer.
• Water. Room temperature, and not straight from a heavily chlorinated tap. Fill a jar, leave it open on the counter for an hour, and most of the chlorine dissipates.
• A clear jar. One quart is plenty. You want to watch the rise through the side, and glass is easier to judge than plastic.
• A scale. Measuring cups compress flour differently every time. An inexpensive digital scale makes the whole week repeatable.

The ratio is simple: equal weights of starter, flour, and water, written as 1:1:1. On day one there is no starter yet, so you begin with 50 grams of flour and 50 grams of water.

Days 1 Through 3: The First Bubbles

Day 1

Stir 50 g flour and 50 g water in the jar until no dry patches remain. Scrape the sides down, then cover loosely with a lid set ajar, or a coffee filter held on with a rubber band, so gas escapes and dust stays out. Set it out of direct sun. Nothing happens for hours. By evening you might see a bubble or two, and that is fine.

Day 2, morning

Expect a thin, pasty mixture with a few small bubbles and a smell like wet flour. Pour off all but 50 g of the starter, add 50 g flour and 50 g water, stir, cover. That is the routine from here on: discard down to 50 g, then feed 50 g each of flour and water.

Day 3, morning

This is the day that gets people excited and then disappointed. The starter often doubles and foams, sometimes dramatically. It's a false rise, driven by bacteria that thrive early and then die back, not by the yeasts you're waiting for. Feed as usual and expect tomorrow to look worse.

Days 4 and 5: The Stall That Fools Everyone

Morning four is deflating in every sense. The starter may be flat, thin, and separated, with liquid pooling on top and a smell of nail polish, acetone, or sharp vinegar. It won't rise much today, and probably not tomorrow either. This is the normal middle of the process, not a failure. The acid-tolerant yeasts are still building up their numbers. Plenty of people quit right here and start over, which only puts them back at day one.

What actually helps

• Keep feeding once a day at 1:1:1, in the morning, at the same time.
• Stir it once midday with a clean spoon to redistribute food and oxygen.
• Find a warmer spot. A starter at 68°F crawls; at 76°F to 80°F the whole week compresses. Top of the fridge, a warm corner, or an oven with only the light switched on.
• If dark liquid forms on top — that's hooch — pour it off or stir it back in. It means the starter is hungry.
• Don't add sugar, honey, or commercial yeast. They change the flavor and hide whether the starter is actually working.

A smell of acetone or vinegar on days four and five is progress, not rot. Furry mold, pink streaks, or orange patches are a different story — those mean starting over with a clean jar and fresh flour.

Days 6 and 7: The Real Rise

Somewhere around day six, usually within a day of the temperature being right, the starter wakes up for real. Feed it in the morning and by late afternoon it has climbed the jar, domed slightly at the top, with a web of small bubbles visible through the glass. The smell shifts from acetone to something closer to plain yogurt, ripe fruit, or flat beer. That change is the sign that yeast has taken hold.

On day seven, move to feeding twice a day, morning and evening, twelve hours apart, still 1:1:1. If it doubles within four to eight hours of each feeding and then falls back on its own, you're there. If it only rises a little, hold that twice-daily schedule for another two or three days before you try baking.

How to Tell Your Starter Is Truly Ready

Rising once is not enough. The starter should do all of the following, two or three days in a row:

• Doubles in volume, or close to it, within four to eight hours of a 1:1:1 feeding at room temperature.
• Holds a domed top instead of a flat, soupy surface.
• Shows bubbles throughout, not just on top, and looks spongy when you lift it with a spoon.
• Smells pleasantly sour — yogurt, fruit, beer — rather than like nail polish or nothing at all.
• Floats: drop a small spoonful into a glass of water. Well-aerated starter floats.

The float test is a clue, not a verdict. A starter that rises reliably but sinks is often just past its peak, so feed it and check again in a few hours. The rise itself is the real evidence.

Feeding Schedule at a Glance

• Days 1–3: one feeding daily, morning. Keep 50 g, add 50 g flour and 50 g water.
• Days 4–5: one feeding daily as before, plus a midday stir.
• Days 6–7: two feedings daily, twelve hours apart, same amounts.
• Temperature: keep it between 74°F and 80°F. Below 68°F everything slows and the week stretches.
• Discard: collect it in a lidded jar in the fridge. It makes good pancakes, crackers, and flatbread.

After Day Seven: Keeping It Going

A mature starter doesn't need this much attention. Once it's dependable, feed it, let it sit an hour, then move it to the refrigerator. Take it out the night before you plan to bake, feed it once or twice at room temperature until it doubles on schedule, and use it at its peak — domed, bubbly, just before it starts to sink.

From the fridge, feed it once a week when you're not baking, discarding down to 50 g each time. If a gray liquid forms on top, it's hungry rather than ruined; pour it off and feed. Neglect it for a month and you can usually bring it back by scraping off the dry top layer and feeding it two days in a row.

And if the schedule slips, don't start over. A missed feeding on day five costs you a day, not the batch. The jar is more forgiving than the instructions make it sound.

Photo: monicore / Pixabay