The gilding step was added to the Daguerreotype process in 1840 by Fizeau. He discovered that when a Daguerreotype was treated in a solution of hot gold chloride and sodium thiosulfate, both its mechanical and optical properties were improved. This improvement in properties is due to the accelerated hardening of the amalgam image particles that make up the image and to the slight alteration of the Daguerreian microstructure that results from the gilding process. In the gilding process gold preferentially replaces mercury over silver, resulting in an uneven dispersion of gold over the Daguerreotype surface with a concentration of gold in areas of high image particle density. Although a protective function has gradually been implied for the gilding process in Daguerreotypes, gilding does not protect Daguerreotypes from silver sulfide corrosion. While gold toning, the modern outgrowth of gilding, does prevent sulfiding, the Daguerreotype presents other problems not found in conventional silver halide systems. The entire Daguerreotype may act as an electrode in the silver sulfide corrosion so partial covering of the silver electrolyte by the non-uniform gold layer is not effective in prevention of corrosion. A uniform coating of gold is a good choice for the sealing of a Daguerreotype from silver sulfide corrosion and its use is described. -- AATA