I'm going to be making a wedding cake-three tiers-with all buttercream. I've been having the problem of a large air bubble forming randomly under the buttercream after i'm all through decorating. Mostly happens on the side of the cake. What causes this and how can I prevent it from happening. I usually fill and crumb coat, then refrigerate for about an hour. Then I ice with room temp buttercream, smooth and refrigerate again for an hour. then I will decorate. It seems that after about an hour, the dreaded bubble starts puffing out. Help! This cake is probably going to sit on display for about 2 hours before being cut. Thanks for your input in advance!

You can get some good ideas/causes/fixes from these threads:
https://www.google.com/search?q=air+bubbles+cake+site%3Acakecentral.com&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a

Most people will probably say your problem is your not letting it settle long enough. However, I fill and crumb coat and let the cake settle over night and the last cake I made got an air bubble!! I really wish I knew what the problem was. I have only had 2 cakes do that but I didn't do anything differently with them....???
BTW, I don't refrigerate mine at all. Maybe if you skip putting it in fridge it will happen less...who knows. Sorry I couldn't help!!

http://cakecentral.com/cake-decorating-ftopict-633571-.html

Read the first post by Leah_s about getting a cake to settle before icing.

Thanks. That thread refers to a fix for the dreaded bulge. To fix the airbubbles, you need to "break the seal" of the icing to the bottom board. After finish icing, run a thin bladed knife between the board and the cake. This was one of the FNCC tips back when I was dong them. Yes, it messes up the bottom edge, so hopefully you've got a border or ribbon for finishing. But I swear it works. I only get bubbles when I forget to "break the seal" and let the cake "breathe."

Someone else suggested using a skewer and poking a whole in the center of the cake which would be covered up by the next tier. That should also work.

i agree with Leah, your cake is so well sealed with buttercream that the expanding air is trapped and forms a cake boil/bubble/blister, what everyou want to call it. I find it is worse if you chill the cake after icing. What i have started doing is taking a drinking straw and remove a plug of icing from the center top, where it will be covered with another cake or even a dowel for transporting. it just gives somewhere for the air to escape. Same as Leahs method, just on the top instead.

THANK YOU, THANK YOU, THANK YOU Leah!

I have had have the worst time lately with air bubbles popping up in my buttercream. I've begun to cringe every morning when I go look at the cake I finished the night before. I came on here yesterday to ask if anyone knew how to prevent them and happened upon this thread.  Just to cover all my bases, I broke the seal of icing at the bottom and poked a hole in both tiers with a skewer.  Looks great this morning! 

I think the only thing I probably should have done is break the bottom icing seal before I inserted the SPS plate.  That seems to be one of the crucial times bubble pop up, I guess because of the air that's displaced by the columns.  Next time I'll be sure to do it in that order. 

Thanks again!

Well- this saved my cake-baking tush today!

yay!!!

There is SUCH a wealth of information on this site that one can almost overlook the problems :)    So glad it is still available