Authoritytgm001125
https://www.loc.gov/pictures/collection/tgm/item/tgm001125
tgm001125Scope NoteCyanotypes that reproduce designs as white lines against a blue background. Introduced in the United States ca. 1876; predominant method for reproducing architectural and engineering drawings by the 1950s; largely discontinued by 1980.
![[4th floor blueprint plan for the Rialto building]](/img/placeholder.gif?1762303493 "[4th floor blueprint plan for the Rialto building]")