Fermentation lock blew off

So I finally brewed my first batch last Saturday. Used Wyeast Activator pack and fermentation began within 8 hours. Noticed some cloudiness in the fermentation lock before going to bed Sunday night but didn't think anything of it. Woke up Monday morning to find that fermentation lock had blown off overnight. Don't know when. I quickly refilled the lock with water and gently set it back on while I sanitized another lock to replace it with. Fermentation was still going very strong. By Tuesday, activity was slowing and now, Thursday morning, is very slow.

I am worried that I may have allowed the batch to become contaminated by having the lock blow off but don't know. Do you think I have reason to worry?

Also, I am thinking that I should move the beer to secondary fermenter this weekend and have ready varying opinions on how long to keep it there but am leaning towards 2 weeks as I've read here seems to be a standard.

I took a hydrometer reading but my instructions told me to look at the potential alchohol scale instead of the specific gravity so I don't know what the SG is. I assume that as soon as the potential alchohol level stops going down that my primary fermentation is complete and I can move the batch to the secondary stage.

I look forward to all your advice and hopefully I will be able to give some to others as time progresses. Next batch is going to be a porter and I can't wait.

Cheers!!!!!

Don't worry the active fermentation should have kept out all the 'nasties'.

Don't worry it is very unlikely that some contaminated your beer when the lock blew off. Next time use a blow-off tube and avoid the problem.
A common plan is 1,2,3 (1week primary, 2 weeks in the secondary, then 3 weeks in the bottle). However many people, including myself, are now starting to leave the beer for 2-3 weeks in the primary and then bottling without a secondary. Either way plan a month from the brew date before drinking any.
SG is directly related to potential alcohol which you can see by looking at your hydrometer and seeing how the numbers line up. When the SG (potential alcohol) is stable for 3 days you are done fermenting but you should leave the beer in the fermenter for at least a few days to a few weeks after it finishes.
Craig

you've got nothing to worry about. happy brewing

Standard answers:
1) Let the krausen drop
2) Take hydrometer readings over 2-3 days
3) Rack to secondary if you wish, or wait a couple more weeks and go straight to bottles.

Oh and blowing off the airlock is ok but risky, I suggest a blow off tube next time.

"Don't worry and have a homebrew"

The same thing happened with me during my fourth brew. It was one of my best to date. The CO2 and alcohol present should be enough to fend of the baddies.

After my popped lock, I moved to a blowout setup. Even though it's a little more cumbersome, I find that it's much less worrysome.

My setup is about 4 feet of 1/4 inch tubing attached to the bottom portion of a three piece airlock. (don't forget to snip off the crossbars at the bottom of the airlock) Then, I run the open end into a pitcher full of water and a drop of satnitizer (I use BTF Isophor.)

You can leave this blowoff on for the entirety of the brew. There is no way that colder temperatures will suck the water into the beer because of the length of the tube.

May the Yeast be With You