I made thick silver sheets by casting scrap with a couple of pure silver cartwheel dollars chucked in to add purity to the mix; and I had sheets 3 mm thick, which I had to hammer down to 1.5 mm by eye using a big beast sheet of inch thick flat steel and small hammers, and turned a hemisphere dome over a three fly-wheel manually used lathe and annealed and beat the silver over the dome and planished (to beat with a high-polished hammer face in a gentle spiral travelling outwards to the then smoothed and polished outer edge). I have a theory that, by using successively finer grits, I can mirror finish the insides so bright as to focalize sunlight and form a laser beam of it hot enough to melt rock. I have the theory that this primitive laser effect helped the aztecs and incas and mayans to create their precise stonework, as well as using granite or obsidian stones (harder than the stones they were working on) as 'hammer-stones' to carve by gentle erosion; which is how nature herself works, using time and tides as the hammers to beat cliffs into new shapes over passing ages.