Making Mirrors for Rolleicord and Rolleiflex

I needed mirrors for a few old Rolleis -- an Automat 2 and a Rolleicord IIc had no mirror at all; an Old Standard had a piece of ordinary mirror, oversized and misaligned; another Old Standard's OEM mirror (dated 1931) had silvering that was almost all gone. I read a suggestion on the Medium Format digest about using mirrors scavenged from a dead SX-70. I posted a want to buy on Craig's list, and got 2 dead ones at $5 each. (Plenty of these are going to be available cheap as SX-70 film is discontinued as of 3/2006.)

After pondering online disassembly instructions:
http://www.chemie.unibas.ch/holder/sx70tech.html
and the need for Torx drivers etc I decided to adopt an Alexandrian approach and ripped it open. It was a pleasant surprise to find it has 2 mirrors...an upper mirror that might be big enough to yield 2 Rollei mirrors, and a smaller lower mirror.

The upper mirror is attached to the roof of the camera by three gobs of a silicone-like goo-glue, two at the wide end and one at the toe.. I carefully sliced through them with an exacto knife, then with the mirror face down on a flat surface I scraped residue away with a single-edged razor blade, and cleaned up remnants with Goo-Gone.

The lower mirror looked difficult as it is stuck to a flexible latticed pivoting screen by a very strong double-sided adhesive film. These mirrors are very thin (about 1mm thick) and therefore fragile, but as the lower mirror was a bonus I decided to see if I could get it off.

Peeling the fresnel mirror film, mostly to see what was going on with the mirror below.

Carefully peeling the support away from the mirror.

Success! I then scraped the adhesive film off with a single edged razor blade, and removed residue with Goo-Gone. Although a little broke off, the unbroken area was sufficient to make a mirror for an Old Standard. I made a pattern by tracing a good mirror onto a piece of card stock. Measurements for various cameras are here. I laid the pattern on the back (unsilvered) side and traced around the edge with a Sharpie marker. At this point I had zero life experience in cutting glass, so I practised with the thin glass part of a Mamiya screen that I had removed the fresnel from to cut down and use in an Original as described elsewhere on this site.

Snapping off surplus mirror: I scored along the marks with one of those little carbide-wheel scorers. As shown in the drawing, I laid the mirror with the score over the edge of a steel ruler, and pressed down on two little 6" rulers with cork bases on either side of the score and pressed down to snap off the excess mirror, distributing the force with my fingertips along the length of the cut. Although for one cut I scored too hard with the mirror on too soft a surface, the unplanned break was not disastrous.