Ok so I had my cake filled, iced, covered with fondant. Putting decorating touches on it, all of a sudden cake started swelling like it was going to pop. I took a toothpick and popped it you could almost hear the air come out. What was that about? In the am it looked even worse. I ended up taking an exacto knife and cutting out part of the cake and covered it w a dot. Please advise!

Yeah - I hate blow-outs. Had one once and almost freaked out.

Most likely the cause is you had pockets of air in your filling, your cake hasn't settled properly, when you put the fondant on it just adds weight and that air needs somewhere to go. I usually put something heavy (a book, board, etc..) on top of the cake when settling and haven't had a blow-out since. But your best defense it to make sure your filling is properly applied with no air pockets.

Another reason is your fondant may not have been adhered well to the cake and you already had a bubble.

Also, remember the temperature of your cake can impact what happens. Just like water/ice, there is slight swelling/shrinking when going from one temperature to another (e.g. from the cooler to room temperature).

There are quite a few posts on CC that talk about these nasty things so you may want to search around and find what others do.

what i find helps prevent this. when u ice ur cake with buttercream put it in th fridge for an hour or so...when u take it out spray it with water not alot just a few sprays then roll your fondant on and put the cake back in the fridge. when i do this it helps alot with the bubbles.

I just had the same thing happen. My cake looked like it had a growth! I had already painted it and now it is smudged. ARGH! I frosted w/ buttercream, let it set over night in the fridge, then pulled it out and covered it. I guess I should have waited longer for it to come to room temp!

I'm with "snowshoe1"--since I've added weight to the tops of my cakes (I use Leah's suggestion of using "floor tiles." Just wish I could find a 10"x10" tile--may have to have someone cut me one.) as they settle overnight, I haven't had a problem with bubbles. I also only put my cakes in the freezer for 7-8 minutes before covering with fondant. I've always had problems icing/covering cold cakes.