A glass adhesive cloth
If the article is just cracked, simply apply glue sparingly glass and let it dry in the sun. Glass is UV glue sensitive and strong dry in the sun. The tail is very thin and seeps into the crack of a discreet but powerful repair. Do not bother using thick adhesive or other adhesive that will be visible and rough to the touch when dry.
If the item is broken, place the pieces out like a puzzle, so you can place them together with glue on the edges.
One by one, put the glue on the broken edges and carefully glue them together according to the directions on the package of glue. It may be useful to have a helper to hold the pieces while binding the edges.
Chips are more difficult to repair. The process involves grinding wheels with Felt and pumice, and usually must be performed by a professional restorer of glass. Sometimes, a small chip can be eliminated very slowly with 600 grit sandpaper, but the surface will not be easy and shape are affected.