I have noticed that the white gel food coloring (Americolor) I use makes my icing thicker. Fifteen drops for that amount is quite a bit more than I use. Have you used this without the white, and do you think it makes a difference? I learned to decorate cookies with glaze, and was astounded by how much easier it is to work with royal icing. However, glaze really tastes so much better.
I have always just poured milk mixed with real vanilla into a bowl of powdered sugar until I get a thick version of the consistency I want, sometimes with a tiny bit of melted butter for extra flavor. Then color it, wait a while, and add more sugar. (It always gets thinner if covered well, and I think it is because a little extra time is needed for the sugar to completely dissolve.) I am looking to try out many different recipes for royal icing, glaze, and a mix of the two.
I hope to compare them side by side at the same time, so environmental factors are the same for all. Do you think the corn syrup makes a difference in the consistency, or just the shine?