>> I have a question about sourdough starter.
...
If your start is active and makes good bread I wouldn't worry too
much about whether or not it has foam on top. Mine doesn't have
"foam" but the whole mass is alive and bubbling.
I think that if you are leaving it two weeks between uses it is
likely to need at least several feedings to get it really active
again. I leave mine about 4 days or so and find that several feeds
are needed, although I'm amazed at how much faster it revives if I
use a little organic rye flour with my wholemeal. It's a real booster.
Jim