Dick Adams wrote:
For reviving and culturing, bleached all-purpose flour is least likely to introduce
unexpected microorganisms (according to me). -- Dicky


For reviving something "old" and not starting a new one - one could also
"sterilize" the flour by spreading it on a baking sheet and then either
put it under the broiler (less evenly distributed head) or bake it for
maybe 20 minutes. Then, keep it in a sterilized container and use it for
reviving the starter.

Besides this - I think that west of the Atlantic, too much attention is
given to starters and trying to keep certain qualities based on a
starter and not how it's being used (parameters temperature, hydration,
time & flour type) to make good bread.

Sam