To make a blueprint, place the tracing in a blueprint frame with the inked side next to the glass and lay a sheet of blueprint paper with the sensitized side next to the tracing. Put the back of the frame in place and lock it in position so as to hold the tracing paper. Expose to sunlight for 30 seconds.
Thomas E. French and Carl L. Svensen Mechanical Drawing For High Schools (New York: McGraw-Hill Book Company, Inc. , 1919) 82
Courtesy the private collection of Roy Winkelman