In a small mixing bowl, combine water, meringue powder, and cream of tartar. Beat until stiff peaks form.

In a separate bowl, mix powdered sugar and gum arabic. Add to the meringue mixture and beat on low, then medium speed until stiff peaks form.

Once the royal icing is ready, divide it into small containers and cover with a damp cloth to prevent drying out.

To adjust the consistency, add small amounts of water until the icing is fluid but not watery. Test by dropping a small amount from a spoon onto wax paper—it should smooth itself in about 10 seconds.

If the icing runs too much, add more powdered sugar; if too thick, add more water.