Etching of daguerreotypes for image reproduction

The present experimental study is concerned with chemical methods for converting daguerreotype images into printable matrices. Insights into the role of the silver-amalgam image nanoparticles in the highlight areas for the preferential etching process in shadow areas. Oxidative dissolution of the highlight areas covered with silver-amalgam nanoparticles was drastically retarded, so that the etching process with diluted nitric acid of the silver substrate in the shadow areas could preferentially take place. The nitric acid preferentially dissolved the silver from the silver-amalgam nanoparticles in the highlight areas so that a mercury-rich layer remained which was passivated by a mercury oxide conversion top layer. This resisted the corrosive attack of nitric acid in contrast to the shadow areas of the uncovered silver substrate where the nitric acid caused substantial etching.