I have used alumina in wax on porcelain for many years and never saw anything like that. I usually just brush is one both sides and the bottom for porcelain.
I can only think that it may have dripped during application. Was your wax white?
For that process, I use the Aftosa wax.
I like it because it is bluish and can be seen. It can come off if you make a mistake and catch it immediately.
Marcia