in the icing on tiered cakes. I have had it happen the last 2 times on a 2 tiered cake. The side blowed out. I stuck a pin in it and pushed the icing back in. I hate when this happens. I wish I knew why it happened. It has happened both times on the bottom tier. I used betty crocker cake mix.
Most of the time it's due to putting on the final coating of BC or fondant on a too cold cake. You really want your cake at room temp before doing the final coat. Or it could be gas or air escaping from a cake that hasn't had time to settle enough before the final coat was put on the cake. I start with frozen cake, fill and crumbcoat it then allow it to sit and settle for 3 hours at least to come to room temp and finish settling. Then I resmooth and do the final coat of BC or fondant. HTH. Cat
It cooled over night. I did not freeze it.
After you filled and crumbcoated it did you allow it time to settle? Many people allow their cakes to settle overnight but I usually just wait 3 hours. I know that some here weight their cakes with a kitchen tile so they will settle faster than that.