A buttercream made with a recipe consisting of butter and shortening can generally sit out at room temperature for up to 2 days.

Icing made with raw egg whites needs to be kept in the fridge, however, icing made with meringue powder can be kept at room temperature.

Icing made with Meringue powder lasts for up to a month at room temperature. I prefer storing icing in the fridge. Use icing made with pasteurized liquid products without 5 days, store it in the fridge. Icing made with egg white from fresh eggs should be used immediately.

When storing the frosting, be sure to cover it tightly; and then refrigerate. If it is not stored airtight it will begin to set. Once the boiled frosting has been spread on the cake, it can be stored at room temperature, but refrigerating it will help keep the frosting soft and fluffy longer.

It’s always best to use seven-minute icing as soon as it’s made and cooled, when it’s at its smoothest and most malleable. Still, it can be refrigerated for a day or so if necessary. If your icing hasn’t reached the correct temperature during preparation, refrigeration will make it break down and become runny.

What to Do With Leftover 7 Minute Frosting

1. smear on spicy gingersnap cookies, and toast the fluff with your new butane torch.
2. smear on your roommate’s box brownies that he frosted with one of your frozen tubs of egg white chocolate buttercream.
3. eat straight out of the tub–not too much though.

Refrigerate. Spoon the mixture into a clean, plastic air-tight container. Do not use a glass bowl that is then covered with plastic wrap as the frosting might pick-up the odors of surrounding food. Secure the lid on the plastic container and store the seven minute frosting in the refrigerator.

Due to these exchanges, seven-minute frosting isn’t a good candidate for a make-ahead option—that’s what buttercream is for! But if you need a quick and simple frosting fast, it’ll get the job done with minimal ingredients and fuss.

If the mixture has not been sufficiently heated, the network isn’t as stable and will eventually break down, turning the icing runny. To ensure that your icing lasts as long as the cake, make sure to stick your thermometer deep into the center of the egg white mixture.

Frosting Stability In the long term, seven-minute frosting stores poorly. It usually deflates within 24 hours, as the egg whites revert to a liquid state and the cake absorbs them. If you need a frosting that lasts longer but will hold up to heat, consider a cooked buttercream or another more stable recipe.

Icing completely dries in about 2 hours at room temperature. If you’re layering royal icing onto cookies for specific designs and need it to set quickly, place cookies in the refrigerator to help speed it up.

If the icing is applied thinly then it should take 4 to 6 hours to dry completely (though the surface will be touch dry quite quickly) but if it is a very thick layer (such as “snowcene” icing on a christmas cake) then it can take a few days to dry completely.

Fortunately, you can prepare royal icing with meringue powder — available at crafts stores and bakery supply outlets — or with pasteurized egg whites, which are available in most grocer’s dairy cases. Both products make perfect — and perfectly safe — royal icing.

Icing completely dries in about 2 hours at room temperature. If you’re layering royal icing onto cookies for specific designs and need it to set quickly, place cookies in the refrigerator to help speed it up. See blog post above for make-ahead and freezing instructions.

Chilling and adding sugar are the two tastiest ways to harden tub frosting. Simply place the tub in the refrigerator and chill for a few hours, depending on the size of the tub, to firm up the frosting. Add sugar to the frosting by first scooping the desired amount of frosting from the tub and placing it in a bowl.

Will Royal icing harden in the fridge? Once you have used it for a project and need it to dry, don’t put it in the fridge because the cold, damp air won’t allow it to set and will make your baked goods go soft. Let the icing dry at room temperature.