HOW THE IMAGES WERE MADE

摘要

Daguerreotypes start as copper plates with a thin, mirror-polished coating of silver that's been exposed to halogen gas (iodine or bromine) to make silver halide. Light hitting this compound knocks an electron loose, which attaches to a silver ion, forming a neutral silver atom. The result is that all the places on the plate exposed to light are clusters of pure silver, and the rest is silver halide.