For several months now I have been having a re-occuring problem with fondant cakes. They are perfectly smooth and tight against cake when I finish them, but overnight they develop huge bubbles underneath the surface, not filling bulges, but actual pockets of air that I have to pull the fondant away from the cake and smooth again (not good if you've already finished the decorative work on the cake), and often they will just move to another area and happen agin a few hours later! It doesn't seem to matter whether I work with the cakes chilled or room temp., what kind of filling I have, whether I have standard or SMBC under the fondant, it keeps happening. At first I thought it was the warm weather, but now it's cooler and it's still happening. Not on every cake, but at least 80% of the fondant cakes. It makes me want to cry! Any ideas why this is happening and what I can do to stop it - please help me?!

Are you making fondant from scratch or using a pre-made fondant? Sometimes when I make my fondant from scratch and don't let it set or rest long enough I sometimes have this problem. Also, I found that if I let it rest for at least 8 hours and then don't "overwork" it when I'm rolling it out to put on the cake I will have less bubbles. This is true with the pre-made too - try not to over work it. Hope this helps. Maybe some others can confirm they have found this to help too. Good Luck!

I'm using bought fondant, and it happens with different brands. I definitely don't overwork the fondant, just enough to make it pliable and easy to roll. They don't occur in the fondant, but under it. It never used to happen to me, which is why I don't understand why it all goes so wrong now!

When we figure out what is causing this I bet many will breath a sigh of relief.
This is like the spots in b'cream. There just doesn't seem to be any answer

When I teach covering a cake with fondant I tell my students to get a corsage pin handy. instead of removing the fondant just poke tiny little pin pricks in the bubbles then smooth over them again.

I also cover cake then let it sit overnight to see if it will bubble up on me, if in the morning it has bubbled up I just start poking pin holes and smoothing out the fondant, it's easier if not decorated first.