Drying Your Sourdough Starter
There are a number of good reasons why you would preserve your sourdough starter by drying it, including if you can’t (or don’t) want to use and/or feed it for a long period of time; you’d like to put some aside for ‘insurance’ just in case your sourdough starter dies (oops!); or you simply want to send it to someone in the post.
Drying sourdough starter is super simple to do: Start with a well-fed, active starter and use a palette knife to spread it in a thin layer over an oven tray that has been lined with baking paper or a silicone baking mat. Allow it to stand at room temperature (the warmer and less humid it is the quicker it will dry) until it is crisp and completely dried through. Then break the starter into small pieces (you can also coarsely crush it), place in an airtight jar (or seal in plastic bags if you are going to send it in the post) and label. It will store in a cool dry, dark place for up to 1 year.
To activate it, add the same amount of water and unbleached plain flour by weight to the crushed starter (30g is a perfect amount to start with). Stand for 12 hours in a warm place (about 23°C is good). Repeat this two more times. On the fourth feed, first discard half the starter mixture and then add the water and flour and continue to repeat this discarding and feeding every 12 hours until it doubles in size in under 8 hours. Your reactivated starter will then be ready to use!