[emeritus]

I have successfully used the special Loctite Glass Bond to mend broken glass items (a 1930's lamp shade and some broken wine glasses, all of sentimental value) . The lamp shade was multicoloured swirls anyway, so the joins do not show, but the joins in the wine glass are visible. The problem is that to make a joint invisible, the refractive index of the bonding medium must be the same as the glass. I believe that the stuff used professionally for repairing digs in car windscreens is matched to the glass and so is virtually invisible. Loctite Glass Bond is cured by UV light and I use "black light" CFL lamps (the type that makes your shirt glow in the dark) to accelerate bonding, as they do not incorporate any UV filtering. Loctite is relatively viscous and is not really suitable for fixing cracks as it will not seep in, but is fine where the pieces are completely detached so that you can apply it to the surfaces to be bonded. Degrease with Meths or IPA before applying the Loctite.