The invention is an improved mercury vapor apparatus for developing daguerreotype photographs and modified daguerreotype methods for the production of holograms and etched semiconductor masks, or other types based on the daguerreotype process. The improved mercury vapor apparatus uses 99.99% less mercury by weight than the traditional inverted pyramid apparatus used by those skilled in the art. This is accomplished by replacing liquid mercury with a metal plate amalgamated with mercury to serve as the source for mercury vapor, providing improved convenience for chemical handling and safety. The mercury vapor apparatus is easily transported and eliminates any risks due to spilled mercury. Furthermore, the mercury vapor apparatus is adapted for developing daguerreotype plates, and other types based on the daguerreotype process, while in the camera plate holder, effectively blocking actinic light from spoiling the plate and eliminating the need for darkroom facilities.