I'm brewing the first batch and was wondering how do you know when it is infected? There is some funky smells coming from it. Now granted, I spilled a little wort when I took the OG and failed to clean it up (I'm on crutches, give me a break) so the infection could be coming from there. But how do you know for certain that a batch is infected? I'm not too worried about my beer, it looks fine but any feedback on this would be great.