1. Feed your starter using equal amounts of starter, flour, and water (1:1:1). In other words, if you have 100 grams of starter, add 100 grams each of flour and water.
2. Let starter ferment in a warm place for about two hours – you should see bubbles and activity. It will continue to ferment throughout the drying process, so you don’t want it to reach its peak here – just get active.
3. Spread sourdough starter thinly on dehydrator trays. Most dehydrators have a silicone mat that fits into the tray for making fruit leather, etc. If yours has that, use it, or cut parchment paper to fit. You can also use an oven-safe tray or rack, lined with silicone or parchment.
4. Set dehydrator to 110º, and let dehydrate for 2 hours, undisturbed. If you are using the oven, use the pilot light, or briefly heat your oven before putting the starter in. Be careful not to let your temperature rise above 115º, which will kill your bacteria and render your starter useless.
5. After two hours, check the starter. If may be dry on top, but still very wet on the bottom. If this is the case, use a rubber spatula to flip the starter over and dry the under side.
6. Let dry another two hours.
7. Check for wet spots underneath, and if you find any, expose them so that they can dry.
8. Once starter is completely dry, break it into small pieces, or blend it into powder.
9. Store in a sterilized, airtight container such as a canning jar out of direct sunlight.

To rehydrate: 

1. In a glass jar or bowl, stir together:

• 10 grams of dried sourdoughs starter
• 50 grams of white flour (use all purpose or bread flour)
• 1 teaspoon of granulated sugar
• 60 grams of warm water

1. Cover with a loose lid or towel, and let sit at room temperature for 24 hours
2. Stir it up, and let sit for another 24 hours
3. On the third day, Add an additional 60 grams of flour, and 60 grams of water
4. Let sit another 24 hours.
5. At this point, you can feed again, and use as normal. But keep in mind that it may be sluggish at first, and take as many as five or six feedings of your starter to start to look bubbly and active like you’re used to seeing.