As you probably know, many clocks have beautiful glass meant to protect the dial, keep dust out of the movement, and keep curious fingers away from pendulums. If your glass should be broken, it creates a great hazard to anyone that may come in contact with it; so please, safety first!
Once you have meticulously cleaned things up (wear gloves!), be mindful that the hard work may have just begun. Getting custom cut glass is becoming more and more difficult lately, with lead times stretching out. Contrary to what we would have otherwise believed, there is no one standing around with a glass cutter in hand waiting for us to walk in the door. Custom-cut glass is becoming expensive and long lead time. And that is for flat glass.
Convex, beveled and other special shapes are another story and each replacement is a project in itself. Off the shelf sizes are becoming rare.
Our best advice: Take care of your glass! Don’t take it for granted when handling, moving, or even opening the glass doors on your clock. You can be assured that replacing that glass is going to be a challenge; more now than ever!