I have tried a few different types of sourdough starters and non of them seem to work for me. I found a super simple recipe for sourdough starter and I though I would share it.
Sourdough Culture
1 cup flour
1 cup milk
Leave milk in a warm place for 24 hours. Stir in flour. Leave in warm place until it bubbles and gets sour. Cover with saran wrap
That is it! Now when I did this recipe I didn't cover the starter. The recipe didn't say to cover it. It still made sourdough starter. It was dry and thick but it still went sour. I decided to refresh it and cover it and then I had the bubbles that the recipe talks about. In my recipe I used milled flour and then sift it through my size 40 sifter.

To replace sourdough culture
1 1/2 cups sourdough culture
1 cup milk
1 cup flour
1/4 cup sugar
Mix together. Do not use for 24 hours. The longer you keep and use sourdough culture, the better it gets. If you can't use the culture for a while, freeze it. When you wish to use it again, thaw the culture, then wait 24 hours or until it is bubbling well.
My mom didn't believe that you could freeze the culture so she took some of mine and froze it. It was frozen for about 2 weeks. Last week she pulled it out of the freezer and thawed it. She thought it was bad because it wasn't bubbling. I told her to refresh it and it is perfect.