This recipe assumes that you have already made your very first starter and you are ready to refresh it because you want to bake. If you don't have a starter see the post "Making your First Sourdough Starter"
This mix is for a low hydration sourdough starter which I keep in my fridge. I find that the drier mix keeps longer so I don’t have to refresh it quite so often. This mix is 2 parts flour to 1 part water. My method is to make twice what i need and split it into 2 jars. One goes straight into the fridge for storage, the other goes to a warm place to ripen ready to be used to make the Bake Starter.
Take 100g of your old sourdough starter from the fridge and discard the rest
Mix together with the other ingredients and split into two jars. Put one jar straight into the fridge for the future
Leave the other jar in a warm place until ripe. It will be ripe when it has stopped rising and just starts to show signs of falling back down.
If your starter hasn't been fed for a while, this may take a few days
If it does take a few days and it doesn't appear to develop properly, discard any liquid or discoloured parts and feed again in the same ratio 2 parts flour to 1 part water
Keep doing this, discarding some of the old and refreshing with new feed until your starter has bubbles throughout the mix and reaches the ripe state described above