I brewed a hefeweizen with a extract kit. Gravity reading was 1.035. I checked on it after around 24 hours and the airlock had been blown of and a lot of foam had overflowed the carboy. I tossed it. Any idea what happened?
Thats surprising given the 1.035 gravity. How much head space did you have in the fermenter? How did you aerate the wort?
I can take a guess. Probably your yeast got off to a vigorous start, and your airlock got clogged, and the pressure blew the stopper out. You didn't need to dump the beer. When the krausen is blowing out like that, it's difficult for infection to get in, so you might've been fine. A couple take-aways: Hefe yeast is often really vigorous, so you want to make sure you start at a low temp. Also, it's often a good idea to use a blow-off hose, especially if you're not going to be able to check on your carboy during that first day or two.
I would assume your hefe kit was supposed to result in an OG of somewhere around 1.048. It's pretty hard to not hit the OG with extract. Only five possibilities (alone or in combination) come to mind... 1) The kit was short on extract 2) Not all the extract made it into the kettle 3) You topped off with water to more than 5 gallons 4) You didn't mix the top-off water with the wort thoroughly before measuring the OG 5) You measured the OG while the wort (and top off water) was still hot, and didn't adjust the reading for temperature. I wouldn't have dumped it. Recovering from an unexpected blowoff is easy. Either use a blowoff hose, or clean up and resanitize the airlock and reinsert (if the krausen has fallen by the time you become aware of the blowoff).
the airlock on my very first batch ever had a blowout. I took it out, cleaned and refilled it with starsan solution, and put it back on the bucket. The beer was fine. Taught me a lesson though. No matter how paranoid you are about how you've f'd it all up, you stand to lose little by letting it finish itself off. You can get a good idea at bottling whether it's completely ruined, or if it has a chance of being good. My first 5.5 gallon batch had a blowout, but I wasn't willing to give up on it too easy. I knew it would be at the very least drinkable when I bottled it. It was actually pretty f'n good! Amazing feeling! Try again and RDWHAHB. Or at least relax, don't worry, have a commercial beer and wait and see how your homebrew comes out before you panic.
It's a good idea to invest in a 3 foot section of 1" vinyl hose, this will fit snuggly into the carboy top, you can prop up a jar of water on a bucket for your blow off system. The large internal diameter won't clog as the krausen enters it, and it can help to prevent a big mess. Nothing more beautiful than watching a violent fermentation, it's so alive, it's more fun than watching seamonkeys.
