From storing piping icing to flood icing it’s important to store correctly. Any meringue based royal icing recipe can be stored at room temperature. On days that I am working with my icing, either flooding or adding details, I leave it on the counter until I am finished for the day and them I store in the fridge.
While storing on the countertop I make sure I have a damp paper towel over the top of my bowl. If you want to save the environment you can use a silicone bowl lid. The goal is to make sure your icing is covered and not exposed to air. If exposed to air your icing will start to dry out and get crusty.
I like to use these Rubbermaid containers, or for a smaller amount of icing I use ziploc bowls. When storing in a container place icing in the bowl and cover with cling wrap or press n seal over your icing, touching the icing for a clean and tight seal. Then place the lid on and pop in the fridge.
Royal Icing can be stored for up to 2 weeks. Piped icing consistency stores the best while flood icing will start to separate and only be good for 3-5 days.