Hello everyone. I have a problem I am hoping someone knows the answer to. I have been making cakes for a while and only the last 2 cakes I have made have had this problem. After my cakes are completed and set aside they develop of pocket of air under the icing causing a bubble. It will deflate if I poke it with a toothpick but then my beautiful smooth buttercream icing is left with small cracks. The icing recipe I use has Crisco, butter, vanilla, powder sugar and a little water to thin if needed. Any ideas why this is happening and how I can correct the problem?

This happened to me a couple times... After I decorate a cake....every time...I take a straight pin and poke holes around the base of my cake where you can't see them.   I do this BEFORE the bubble appears.   It has happened with me whether I use crisco/butter recipe or straight Crisco.   I'm sure it's due to the temperature change from the frig to counter.  Gasses are building up...poke holes as soon as you decorate, then your pretty smooth icing won't be disturbed. 

Thanks so much for the idea! I will be icing my grandmother's 100th birthday cake tonight and will give this a try! 

Yes, after seeing pictures of my cakes that people sent me with a bubble I freaked out and swore that would never happen again.   I am still trying to get in the habit to poke holes on every cake...every time.  A step I just recently implemented.   Good luck on your grandmother's cake.   Awesome she is 100!!!