Thanks very much EverlastingSweets,
Actually, most of my royal dries into a matte finish. But some colors--like the red in Anne B's dress, dried to a very shiny, and spongy finish!!! It's weird but I'll assume that certain colors have different chemical properties. I mixed a few different reds for that dress so I don't even know which one dries shiny. I could write a whole page on the quirks, oddities, and extreme frustrations I've dealt with just on the subject of royal icing!!!!
So I, along with you would love to know a good additive to get that glossy look when I wanted it. I've used corn syrup in the past but for some reason that I can't recall now, dumped it. But I know that lots of cookie decorators use it routinely. Time for us to experiment some more!!!