For the best results, feed your sourdough starter before drying it. Allow it to reach peak activity (when it has at least doubled in size after feeding, but hasn’t started to deflate yet) before collecting some of the starter to dry.
Once it reaches peak activity, take some of the wet starter from the container. Use a spatula to spread the wet starter out in a thin layer on a baking sheet lined with parchment paper or a silicone baking mat, or on a food dehydrator tray liner. The more thin and evenly you spread it, the more quickly and successfully it will dry. (For reference, about 1 cup of starter will cover a 14 x 14 inch tray)
Dry the starter in a food dehydrator set to 105°F or less (heat will kill the starter culture) OR set the tray out (uncovered) in a cool, dry and well-ventilated location to air dry. Tip: If your oven has a convection fan, put the tray of starter in the cool oven to air dry (oven off, fan on).
Allow the starter to dehydrate until it is completely dry, brittle, and snaps when bent. The time it takes to fully dehydrate sourdough starter depends on the method you use, how thick you spread it, and the ambient humidity in your kitchen. We usually run our dehydrator on 95°F for about 24 hours.
Once it’s 100% dry, you can break up the dehydrated starter into chips or flakes, or grind it into a powder in a blender or food processor.
Store dehydrated sourdough starter in a cool, dark, dry place inside an airtight container. It should stay viable for many years.
To use the dry starter, you must reactivate (reconstitute) it back into wet active starter first. Follow these instructions or google "Homestead and Chill reactivate dry starter" to find them.