Experts and BHG readers answer.
What is a crumb coat?
The crumb coat is the first layer of icing applied to cakes. It is a thin layer—so thin that you can see the cake through the icing—that is intended to smooth out imperfections and make cake crumbs stay on the cake and not in the icing.
Once a cake is crumb-coated, it is then refrigerated for about an hour to set the icing and fully adhere the crumbs to the cake. Then the final decorative layer of icing is applied over the crumb coat—and because it goes on over a smooth base coat, the icing goes on flawlessly.