What is "crusting" bc and in what situations would I use it?

If it ISN't a crusting one it stays soft and for me hard to smooth out. If it IS a crusting bc then after putting on cake let it sit for 15 min and it sorta forms a crust and you can smooth it with a viva paper towel. I like the crusting because I want to smooth it out completely.

What makes an icing crust is the amount of fat to sugar. The more sugar, less fat the more likely it will crust. The length of time it takes to curst will depend on the recipe used & the humidity in your area. Not all will be ready to smooth in 15 min. Some much less and some a b it longer

B'cream that does NOT crust will remain soft to the touch and is easily messed up when applying decorations.

crusting BC is also helpful in flower making, borders, stringwork, etc as when it dries (aka "crusts") the crusting process helps to hold the shape.