Drawing showing the Print Room in the Mechanical Laboratory (Cocke Hall), 1896 McKim, Mead & White, architects; signed by L.C. Allen, draftsman Blueprint, 20 ¼ x 22 ¾ in. University Archives (RG-31/1/2:2.872)

Although “blueprint" has become a general term for any architectural drawing, it refers to a very specific technology closely related to photography that architects began using in the late 19th century. Paper or some other material is coated with a light-sensitive chemical compound to serve as a base. A drawing made on thin paper is then set on top of the treated base and exposed to sunlight. Much like a photographic negative, this exposure creates a negative image: the lines of the drawing turn up white on the base below, while the rest of the base turns the trademark blue.

This blueprint--which shows the light-filled printroom on top of Stanford White’s Mechanical Laboratory (Cocke Hall) where engineering students created blueprints--is a section: a type of architectural drawing that shows a building as if cut from top to bottom by an imaginary knife and then splayed open. Much like the way a dollhouse allows one to view inside, a section clearly displays the internal structure of a building.