One of the most asked and experimented with in the alcohol ink communities is all about sealing tiles and YUPO paper.
1. Many artist swear by Krylon Kamar for at least a first coat. I now do this also. I like that it does not disturb my signature or the painting. I usually do two coats.
2. Next I use Krylon Triple Thick Crystal Glaze. I may use several coats. Spray lightly from about 12 inches away. Let each coat dry thoroughly before adding another coat. Once I seal the tiles I let the art cure for about a week before letting anything touch it.