Honest Bread
Bake at home · Guide 1

Make a sourdough starter

TL;DR

Mix 50g wholegrain rye flour with 50g water in a clear jar. Once a day, keep 50g of the mixture, bin the rest, and feed it 50g flour and 50g water. Keep it somewhere warm. Around day 7 it will double within a few hours of feeding, and that is a starter ready to bake with. No bought culture, no special water, no secrets.

Baker’s flour-covered hands shaping fresh sourdough dough on a wooden bench
The oldest raising agent there is

A sourdough starter is nothing more than flour and water that you keep alive. Wild yeast and friendly bacteria live on every grain of flour already. Your job for one week is to feed them until they outnumber everything else in the jar. No bought culture, no grape skins, no magic.

Every baker on this site keeps one. Some of their starters are decades old. Yours starts on a Tuesday.

What you need

  • A clear glass jar of roughly 500ml to 1 litre, with a lid you can rest loosely on top
  • Digital scales that read in single grams
  • A bag of wholegrain rye flour, the easiest flour to start on
  • Tap water. If yours is heavily chlorinated, let it sit out for an hour first
  • A warm spot, ideally 21 to 24C. The top of the fridge or near the boiler works

The seven days

Day 1. Mix 50g rye flour and 50g water in the jar until no dry flour remains. Rest the lid on loosely. Walk away.

Day 2. You may see a few bubbles, you may see nothing. Either is fine. Keep 50g of the mixture, discard the rest, and feed it 50g flour and 50g water. This keep-feed-discard move is the whole method, once a day, same time if you can.

Day 3. Often the most dramatic day, a big bubbly rise and a smell somewhere between beer and old fruit. Do not get excited, this is a bacterial false start and it will collapse. Feed as normal.

Days 4 and 5. The quiet days. The false start dies back and the jar can look dead. This is where most people give up, and they are usually two days from the finish. Feed on schedule.

Day 6. Real activity returns, smaller bubbles, a cleaner sour smell, a rise that holds. Feed as normal.

Day 7. Feed in the morning and watch. If the starter doubles within 4 to 8 hours and smells like yoghurt rather than nail varnish, it is alive and it is yours. Give it a name if you like. Most bakers do.

Reading the jar

  • Grey liquid on top. Hooch. The starter is hungry, not dead. Stir it in or pour it off, then feed.
  • Nail varnish smell. Very hungry. Feed twice a day for a day or two.
  • Pink or orange streaks, or fuzzy mould. The only genuine death sentence. Bin it, wash the jar in hot soapy water, start again.
  • Flat but smells fine. Too cold. Move it somewhere warmer and give it a day.

Keeping it alive

Once the starter is established you do not need to feed it daily unless you bake daily. Lid on, into the fridge, and feed it once a week. The night before you bake, take it out, feed it, and leave it somewhere warm. By morning it will be ready for the first loaf.

And when you want to taste what a starter can really do in experienced hands, the sourdough bakers in the directory have a head start of a few thousand loaves.

Answer engine

Questions, answered

Do I need special flour for a sourdough starter?
No, but wholegrain rye makes the first week far easier. Dark flours carry more of the wild yeast and bacteria the starter is built from, so they get moving faster and more reliably. You can switch to feeding it strong white flour once it is established.
Why do I have to throw half away every day?
Because the feeding ratio is the point. A starter needs fresh food in proportion to its size, and without the discard you would be feeding a bucket of starter by day seven. Discard is not waste either, it goes into crumpets, pancakes and flatbreads.
There is grey liquid on top of my starter. Is it dead?
No, that liquid is called hooch and it just means the starter is hungry. Stir it back in or pour it off, then feed as normal. The only time to bin a starter is visible mould or pink or orange streaks, which mean the wrong bacteria won the race.
My starter bubbled on day 2 then went completely flat. What happened?
That first surge is normal and it is not yeast. An early bacterial bloom produces a burst of gas, then dies back before the real culture establishes. Keep feeding on schedule through the quiet days and the true rise appears around day 5 to 7.
How do I know the starter is ready to bake with?
It should double in size within 4 to 8 hours of a feed, smell pleasantly sour like yoghurt or beer rather than like nail varnish, and hold a dome of bubbles on top. When it does that two days running, bake.