If you didn't have anything in your airloack at all, then you'll definitely want to clean it out and put a sanitized liquid in there to act as a buffer. I use cheap vodka, and haven't had any issues, since the alcohol adds an additional barrier against foreign nasties. Just make sure to sanitize your air lock before you reinstall it, otherwise you're asking for trouble. I had a minor foam up some time last night, actually, and some of my pyment made it to my airlock. Not enough to have a full blowout, but enough to prompt me to change out my airlock with a fresh one. As a bonus, I had a nice little shot of grape flavored vodka to make up for the annoyance of having to clean my airlock. It tasted delicious, in case anybody was wondering. ;~)