Here's the mirror showing the bracket on the right side about to detach.
To begin the repair, I took it off the mirror by melting away the existing solder and foil.
Then I took off the existing metal channel on the side, which had bent slightly.
Here I've replaced the metal channel with a new piece, which I cut to size.
To prepare for the re-attachment, I used steel wool to clean off remaining patina from the area.
Here's the partially refurbished bracket, ready for re-installation.
Along the seam where the bracket will be re-installed, I put down a series of solder beads.
On top of the beads, I lightly soldered on a strip of flat braided reinforcement wire. It's 1/8th" wide, the same width as the glass. By using this wire, the bond will be much stronger than without it.
Next I positioned the bracket on top of the reinforcement wire. When the soldering iron was applied, the bracket bonded to the wire, and thus to the mirror as well. Then I added more solder to the sides, as additional reinforcement.
After I smoothed out the soldering, I applied black patina to the solder, as shown. I checked the strength of the left bracket and saw that it was also beginning to loosen. So I repeated the process on the other side.
And here is the mirror, with both brackets now firmly in place.
Another view of the finished project. Thanks for finding me, Marita. It was a pleasure doing this repair for you .. May you enjoy it for many more years to come.