Although modern-day silvered glass mirrors have pretty much destroyed the market for bronze mirrors, these highly polished pieces of metal once were the pinnacle of mirror technology. Due to the laborious process required these mirrors saw use essentially only by the affluent. That said, how hard would it be to make a bronze mirror today with all of the modern technologies that even a hobbyist can acquire for their shed? Cue [Lundgren Bronze Studios] giving it a shot, starting by casting something flat-ish to start polishing.
Just getting that initial shape to start polishing is a chore, with hammering out the shape possibly being also a viable method. When casting metal it’s tricky to avoid having air bubbles and other defects forming, though using a sand mold seems to help a lot.
After you have the rough shape, polishing using power tools seems like cheating, but as you can see in the video even going from 50 to 8000 grit with a rotating disc left countless scratches. Amusingly, hand sanding did a much better job of removing the worst scratches, following which a polishing compound helped to bring out that literal mirror finish.
A quick glance at the Wikipedia entry for bronze mirrors shows that a tin-bronze alloy like speculum metal was used for thousands of years as it was much easier to polish to a good mirror finish. The metallurgy of what may seem like just a vanity item clearly goes deeper than just polishing up a metal surface.
Kudos for the effort and the pretty good result.
He made his life way harder by starting from a cast. If he had bought a bronze disc that was cut from rod stock using modern tools it would have gone way easier. He probably could have got close to that result by polishing alone.
There are a few reasons why you shouldn’t do this, but it is admirable to try. There are machines that can do this type of machining/polishing but they cost more than you’d ever wish to spend. I would love to see a follow-up with speculum. Is it really that much easier?
So back in ancient days, you went down to a store and ‘bought’ a bronze disk and started making a mirror from there???? :) ha! That said, I think in the interest of the video, trying to duplicate how the ancients may have made a disk to begin with — was interesting way to start the project :) . Makes you appreciate what it must have took 1000s of years ago.
He should’ve just went to the store and bought a mirror, duhhhh!!???!!
I realized what I might have written could sound dismissive. He did a good job, despite his technique lacking early on, this is hard work. I think it’s important to say the surface roughness of a true mirror finish, at least for optical applications is literally atoms of variance.
Just a few more items and he will be ready for the Kraken