Brandon's Ultimate Guide to Sourdough Starter

Last updated on August 9th 2025 by Brandon

The Starter

Sourdough starter is a live culture of yeast in a flour/water mixture. The yeast feeds on the sugars and produces a few byproducts, namely CO2 and acetic acid. The CO2 is obviously what gives bread its volume and texture, but the acetic acid offers a deeper flavor and a little tanginess to the bread.

The yeast you buy at stores has been selectively bred to produce CO2 much faster, allowing for the dough to rise faster. The yeast in sourdough starter is “natural yeast” found in the environment, so it takes much longer to rise, typically 8-12 hours. The acidity takes time to develop, so the longer rise time is crucial to sourdough’s distinct flavor.

Caring for your starter

As your starter sits there the yeast are eating up the sugars, eventually they will run out and start to die off since there is not enough food and too much acidity. At room temperature it is recommended to feed the starter about once every 24 hours. This would be far too much for most people, which is why we store starter in the fridge. The cold temperatures cause the yeast to slow down, in the fridge it is recommended to feed them once every 7 to 14 days.

When you are ready to make bread you will take it out of the fridge and leave it at room temperature for around 8 hours. The yeast will increase in volume by at least double and appear very bubbly, this is referred to as “active starter.” You’ll then take some of this active starter and use it to make bread!

Feeding your starter

So you’re ready to make bread, how exciting! Start by taking whatever you need for your recipe, but always make sure to leave some behind. Then you will feed your starter as follows:

  1. In a clean container, weigh 75 grams of starter
  2. Add 75 grams of water and 75 grams of flour (you may use any kind of flour)
  3. Stir it up well so that the yeast is evenly distributed
  4. Put a lid on it and put it back in the fridge!

The key here is to follow a 1:1:1 ratio by weight. You can start with any amount of starter you want, and you will end up with 3 times as much starter. It is helpful to plan ahead and minimize waste. My usual recipe calls for 100g of active starter, so if I start with 75g of starter then I will end up with 225g, which gives me 100g to make bread, 75g for the next batch and around 50g of discard. I could also start with 50g which would give me no discard, but you always want to over-estimate a little because some starter will be stuck to the sides of the jar.

Discard

Once you’re done feeding you may or may not have extra starter left over. This is called “discard” and can either be tossed out or saved. If you look up “sourdough discard recipes” you will find hundreds of amazing baked goods that you can make with discard, so I would encourage you to save it! If you don’t want to do that then you can always plan ahead and try to minimize the discard. Discard will keep in the fridge for a week or two, if it develops a layer of liquid it’s time to throw it out.

Is my starter dead?

Life gets busy and sometimes we forget about things; I've been there. First things first, if there is a layer of clear or grey liquid on top of your starter dump it down the drain. This is the byproducts of the yeast and we don’t want it. Next, you want to do a feeding immediately (without letting it rest at room temperature). The discard from this starter is not going to be useful for discard recipes, so you should dispose of that also. The newly fed starter should sit out at room temperature for about 8-12 hours until it is active again. It may not be quite as active as it usually is, but that’s okay. You can still bake with it, it just may not be quite as lofty as usual. If you prefer you can do another feeding back-to-back, after the second feeing it should be alive and well.

Baking tips

Check back on this page in the future! I will be updating it with photos and a beginner recipe soon. I will also add a printable PDF version!