Dry plate

From Silvergrain Research

Gelatin dry plates are usually in-camera negative material used similarly to today's sheet films, except that their substrate is glass, not film. There are some positive plates, which are exposed with a negative image to make transparency. Positive plates are usually fine grained bromide emulsion with shorter toe than negative emulsions.

Glass plates are highly archival but they are heavy, hard to handle and fragile to impact shocks.