im sure there are tons of forum post about this already but i cant seem to find one so i had to ask...

the last 2 cakes i have made have formed these big air bubbles on the top of them. Can someone explain to me why this keeps happening? and what i can do to prevent it?

here is my step by step process of how i did the cakes just so maybe someone can tell me if im doing something wrong that is causing the air bubbles:
I bake the cake and let it cool completely. i then fill, stack, crum coat then put in the fridge for a bit. I then finish up the icing on the cake. On both cakes i did a FBCT on top, i took that out of the freezer and then put it on top of the cake, then put the finishing touches on the cake. I then let it sit out to crust. When i woke up the next morning it was crusted but an air bubble formed on the top right of the FBCT...

should i not let it crust? im wondering if the temp change from being in the fridge plus the FBCT being in the freezer to then sitting out at room temp may be causing the air bubbles.
Someone else suggested i bake, tort it and crumcoat it then let it sit at room temp instead of putting it in the fridge at all... but thats not going to help the FBCT that has to get cold in order to put it on the cake lol

any tips or suggestions would be greatly appreciated!! thank you!!

I never put cakes in the fridge, so I can't help with that part.

I do think you need to let your cake sit out at room temp (unless there is something in it that just has to be kept in the fridge), after you get to the crumb coat stage. Your cake needs to settle before you add the icing.

The FBCT goes in the freezer to get hard to put on the cake, your cake doesn't have to be cold to put it on it.

http://cakecentral.com/cake-decorating-ftopict-722649-air.html+bubbles+buttercream

http://cakecentral.com/cake-decorating-ftopict-717735-farts.html

http://cakecentral.com/cake-decorating-ftopict-671114-farts.html

http://cakecentral.com/cake-decorating-ftopict-655995-farts.html

http://cakecentral.com/cake-decorating-ftopict-649184-farts.html

The only thing I'd like to add is often bubbles develope because there is air trapped under the icing.; In this case I have a feeling you did not apply the FBCT solid enough - not sure how to say it. Maybe you needed to press down some to adhere the transfer to the cake icing better. Haven't done many FBCTs but I think it would help to put a thin solid layer of icing on it before laying it on the cake?

I have never had a problem with air bubbles appearing with buttercream. I have had problems with fondant bubbles but I think I have found that temp/climate change effects them (air conditioned shop then 110+ degrees w/high humidity). Other than freezing my cakes after baking them I never refrigerate unless cake has to be due to fillings or icings. When stacking cakes I also lay wax paper on each layer and press. I do this with each I add. HTH