When you have a small amount of damaged stained glass it is best if you can have it repaired in situ. The time and effort of removing the panel, transporting it to a studio for repair, and then refitting it is substantial.
This is why I try to carry out repairs on site for people where possible. Usually if there are only one or two broken or cracked pieces, this should be possible. For more extensive damage the only option is to remove the whole stained glass panel and renovate it on a flat surface.
Recently I was asked to repair a stained glass window in Surrey. It was a small piece in a front door that had been cracked by a bunch of keys.
The client had emailed me photos of the door and damage but it was difficult to tell what colour the glass was. Therefore I took a selection of different stained glasses with me for the client to choose the nearest match.
Once the replacement glass was selected, I set about removing the damaged pieces. I scored the remainder of the broken piece and tapped it to break it up for easier removal. I took care to extract the tiny bits that inevitably get stuck in the corners.
In order to fit the new glass, I had to open up the leads around the missing glass.
Next, I measured and cut the replacement stained glass piece. I took my grinder with me to refine the shape. This is often a slow and fiddly part of the process.
Once the glass was the right size, I fitted it in place and carefully pushed the leads back to hold it. Of course it was still very loose, so I filled around the glass with leaded light cement. This is a sticky process, and particularly awkward when working vertically.
Finally, the repaired area was cleaned inside and out.
The cement takes some days to go off so I advised the customer to close the door carefully for a while.
She was very pleased with the repaired stained glass.