Rubber Stopper Won't Stay In Carboy

I am on my second batch of brew and I encountered a problem I didn't have the first go around with the rubber stopper.

After I pitched the yeast into my glass carboy I put the rubber stopper in, but the stopper refused to stay flush in the carboy. It just slides a little out after just a few seconds. It's strange particularly since when I first brewed it was in so tight I had a tough time getting the stopper out of the carboy.

The beer has been pitched for a couple of hours now, and the stopper is pretty solidly in, but it slides up about 1/8 to 1/4 of an inch. Should I be concerned about a blow-out? As much as I love beer i can't stand guard all night to make sure the damn thing stays in.

Please advise...

If the stopper is wet with sanitizing fluid, or even water, and the carboy is wet, it does tend to slide. Once it dries, it'll stop that. I sometimes take a paper towel and dry the stopper if it's still wet when I go to insert it. I've learned to let it air dry, for the most part!

That's why I switched to Carboy caps. They snap on regardless of how wet they are and they stay on.

carboy caps work good, Dry it off with a very clean towel or paper towel
You can also use some tape to make it stick until it dries

I spray the area around the stopper with starsan and then take a doubled-over 2-3" strip of plastic wrap and stuff the stopper in, and then wrap it real tight - stretching the wrap in place ala shrinkwrap style over both the stopper and the top of the carboy so it holds the stopper in place; never had a problem.

I just sit and hold it during primary fermentation.

Thanks very much for the (mostly) helpful responses! It seems to be securely in place.

BuffaloSabresBrewer said:

I just sit and hold it during primary fermentation.

Click to expand...

Are you available next Tuesday? I'm brewing, and I need a carboy bung holder. I pay well.

YooperBrew said:

Are you available next Tuesday? I'm brewing, and I need a carboy bung holder. I pay well.

Click to expand...

Yes Im available. Do I get the same treatment the Brazilians got?

YooperBrew said:

If the stopper is wet with sanitizing fluid, or even water, and the carboy is wet, it does tend to slide.

Click to expand...

I've been playing with both starsan and iodophor, and it seems to me that starsan exhibits more of the "slippery stopper" syndrome. Iodophor-sanitized stoppers can squeak from friction when you put them in.