Fortifications at Manassas / negative by Barnard & Gibson ; positive by A. Gardner.

Illustration showing Union soldiers inspecting a former Confederate fortification.

The albumen silver print is a photographic printing process that was widely used in the 19th century. It involves coating paper support with a mixture of egg whites and salt, which creates a glossy surface to hold light-sensitive silver salts. The paper is then sensitized in a solution of silver nitrate, and exposed in a camera or under a negative. After exposure, the print is developed in a solution of gallic acid and silver nitrate, which reduces the silver salts to metallic silver and creates the final image. The albumen print process was widely used for commercial and fine art photography in the 19th century and produced high-quality, detailed images with a distinctive glossy finish.