All these backflips are very well, but I invoke Ockham’s Razor. The overwhelming odds are that a mirror in a headboard is made of glass in a wooden frame. And most large mirrors I’ve dealt with are backed by plywood. It’s very unlikely to warp concave enough to focus the sun to ignition. Magnifying mirrors, glass doorknobs etc are a completely different story, they are lenses that can focus light. Single flat mirrors can’t.
