A process by which photographs are permanently vitrified onto ceramic or enamel surfaces. The end product was used for jewelry, ceramic objects, commercial decorative novelties, and permanent portraits applied to tombstones. Several methods were invented in the mid-19th century by as many individuals. The substitution processes introduced by Du Motay involved making a collodion transparency on glass from a negative. The image was toned with gold, platinum, or another metal and then transferred onto the final ceramic or enamel support. When fired, the collodion binder burned off , leaving the metal image fused to the vitrified support. The other methods were based on the bichromated colloid work of Poitevin. A carbon-transfer print made from a tissue bearing finely powdered glass could be applied to the final support and fired. A variation based on the dusting-on process relied on coating the final support with bichromated sugar. After exposure in contact with a negative, the sugar was selectively hardened where exposed to light, allowing fine powdered glass to stick preferentially.