Hi, again, I'm not sure what you mean by "sealing", or about the second part of your question ("Or can you seal?"), which seems like the same question as your first . . . but if you are asking if you need another agent or "edible glue" to stick luster dust on a dry royal icing cookie, the answer is no. If you dust it on with a dry brush, the dust will adhere in a very translucent (light) way, leaving a soft sheen. It can wipe off, though, if you run your fingers or something else over it rather forcefully. I hope I've answered your question, but if not, please try re-phrasing it. Thanks!