An obvious first question when it comes to Sourdough is, "So how do you start a sourdough culture?". Interestingly, many members of our community have never had to do it since we've shared some of our existing starter with them. Even those who have started their own have only ever had to do it once since a sourdough culture is a perpetual living microbial ecosystem. As long as it has sufficient feeding (with flour) it will continue to live (and even outlive its baker).
A comforting thought is that sourdough cultures have been around longer than humans and have found their way into all sorts of wet grains fermenting them and sending out spores that travel and find new grains to ferment. Make no mistake, if you have wet flour and wait long enough, you will have microorganisms fermenting it. The trick is to have the patience to enable the "right" organisms the time to establish themselves and acidify the wet flour (the dough) so that they exclude other competing micro-organisms. This generally takes 1 week.
Below is an example of a technique Keziah (a member of our community) used to start a sourdough culture:
We used Eureka white bread flour.
Day 1:
Day 2:
Day 3:
Day 4:
Day 5:
Day 6:
Day 7:
See also the page on Starter Care for additional tips on feeding times/ ratios