Well, we’ve had our first casualty of the season. I dropped and broke one of my favorite blown glass ornaments. Waaaaaa!
What’s the best adhesive to mend clear glass? It has to be easy to control, dries clear, and is non-yellowing.
Cyanoacrylate (Crazy Glue) is good for that if the pieces are tight fitting. Otherwise epoxy or clear silicone. However, blown glass ornaments can be made of pretty thin material and cyanoacrylate won’t really work. Sorry to here it got broken. One of our Christmas traditions is me juggling glass ornaments, haven’t broken one yet, while juggling anyway, broke one just putting it back in the box afterwards.
Thanks, TriPolar. I think it will have to be epoxy or silicone. I appreciate the advice. 
I would think the stuff used to attach the rearview mirror to the windshield would be good stuff.
Attaches metal to glass and is non-hazing.
I never used it though, so…
Do not use silicone you will not get good results and it will yellow. Use UV glue like Aquadementia suggested. The bond will be stronger than the surrounding glass. It will not set up until exposed to a UV light source. Be careful not to let any air bubbles remain between the two pieces and clean all excess with alcohol before exposing to UV. Clean and dry with heat all surfaces before bonding.
UV glue will work great if you have the proper UV light source. Otherwise the bond may never set right. I’ve had silicone glue on glass for decades that didn’t yellow. It isn’t absolutely clear, but you’d have most of it on the inside of the ornament, just like with epoxy. Any that squeezed through the crack can be trimmed off.
You can set UV glue with direct sunlight. It is also UV that yellows silicone if the piece is kept inside away from direct sunlight it can last for years. Different formulations of silicone will age at different rates as well.