rachel - from east windsor, NJ
A stiff consistency icing will help you pipe roses and borders because it stands up. Refrigerated buttercream will be stiff, not because of the consistency, but because of the temperature. Cold butter and shortening will be nearly impossible to pipe through a decorating tip. Next time, make your buttercream as you normally would. Put some into a coffee mug, and insert a metal spatula straight down into the icing. If the spatula falls or leans to the side, your icing is too loose. Add more sugar to firm it up. If the spatula stands straight up in the icing, it is considered stiff enough to pipe roses. There will be no need to refrigerate this icing, and it will be firm, but much easier to pipe.