Jeweler-quality Nikolas Clear Lacquer protects from oxidation, perspiration, sulfur and abrasion, plus protects heat patinas and other colors on silver, copper, brass and bronze!
Envirotex Spray Sealer works great to protect just about everything we've tried it on, but follow instructions carefully or you'll get spots on some types of colorants.
Renaissance Wax is both a cleaner and a polish. It is museum quality, but use carefully!
Use GlazOn as a protective layer between multiple colors of StazOn inks (or other solvent inks) to avoid blending or muddying of colors. Great for use on non-porous surfaces like metal and acrylic. Also can be used as a collage medium for adhering glitters, fibers, micro beads and more, and as a finishing layer to seal artwork.
Ranger Glazes can be used as a sealer for metals to prevent oxidation, or mixed with Vintaj patinas to create translucent tones.