Whether you're gluing wood to a mirror's surface to frame the mirror, create a decorative pattern, add panelling over the mirror's face or for some other purpose, the process is similar. A mirror's silvering is attached to the back of the mirror, beneath the mirror's glass. Because the silvering is projected by the glass, special mirror glue such as mirror mastic is unnecessary if you're gluing wood to the front of the mirror. All you need is strong, clear epoxy glue.
Squeeze the epoxy out of the tube and apply it to the back of the wood.
Affix the epoxy-covered backside of the wood to the mirror's surface.
Hold the wood in place and affix a strip of painter's tape over the wood piece to keep the wood from drifting while the epoxy dries. Attach the tape to the mirror, then over the wood piece, and back onto the mirror. Allow the epoxy to dry according to the directions on the packaging.
Remove the painter's tape.
When choosing wood to glue to the mirror, remember that your mirror will reflect the back edge of your wood piece, so it must be finished to make it match the front of the wood. Test your glue with scrap pieces of wood and glass. Glue the scrap wood to your scrap glass and allow the glue to cure for as long as its packaging recommends. Use the glue for your project only if you're satisfied with your test piece's results after its curing time. Use a marine epoxy if you're attaching a wood frame to a bathroom mirror.
Use epoxy in a well-ventilated area and avoid touching it with your bare fingers.