Dull or Bumpy Icing
Most of the problems I’ve encountered with royal icing can be solved by keeping the iced cookies in the right environment. In order to get a smooth, shiny finish on your flooded cookies, make sure to dry them in front of a fan. Or, better yet, keep the cookies in an air conditioned room. Humidity will cause the icing to dry slowly, which will make it become porous, dull, fragile, and sometimes leave you with a bumpy and uneven surface. Dull or bumpy icing can also be caused by icing that is too thin, so make sure your flood consistency is not too runny.