An inevitable problem when removing leaded glass from a rotten window is that the solder can break at the joints and/or the edge came breaks away. Generally the longer the glass has been in place the more likely this will be the case. Repairing and in some cases replacing sections is a time consuming job.
Once the glass is out repairs can commence.

Edge came that has broken

Step1. is to remove all the old putty from the lead with the glass laid flat on a board which has two pieces of wood screwed down. One so that the base or top of the glass can be laid tight against it and the other piece of wood along one of the edges.

Breaks in solder joints

Step 2.is to inspect each joint and to arrow these so that I know which joints need to be re-soldered

Wire brush the solder joint and the adjacent lead

Step 3.is to wire brush the solder joint and the adjacent lead clean of all dirt so that the lead is shiny this allows the solder to fuse with the lead.

Step 4. If required I need to hold tight the glass against the screwed down wood by either tapping in some hoarse shoe nails or by screwing down further battens. This is so that the whole piece remains static during soldering.

Soldering now commences.

Step 5. Soldering now commences.

Edges now need to be inspected and re-puttied

Step 6. All the joints along the edges now need to be inspected and re-puttied using a special putty cement and chalk dust.

Brushing and darkening the new solder with grate polish

Step7. Involves brushing in the putty and darkening the new solder with grate polish.
The whole process then needs to be repeated on the other side of the unit.
With replacement of lead came along the edges the above takes place once the old lead has been removed and the joints prepared to accept the new came.
There are numerous sizes of came so I have to measure carefully the width and profile, profiles are usually rounded or flat to match the original.