I have delivered wedding cakes and upon standing the frosting will develop an air bubble underneath. I know how to fix it by poking it and getting the air out, but does anybody know what causes this and how to prevent it from occurring?
Make sure your cakes are not frozen when you ice them, condensation can build up and cause a bubble.
Make sure you let your cakes settle for several hours (I let it go overnight) after filling to allow the cake to settle.
Too much liquid in your icing can cause this, as well as high humidity.
Take a pin and poke some holes in the cake. I do it towards the bottom. If I were doing a 10" layer for example, I would probably poke about 4 holes near the bottom. This will allow and air building up to escape. You really should not get "blow outs" if you do this. I do it on my fondant cakes, too.