Wallis, Rolland S. [from old catalog], Iowa state college of agriculture and mechanic arts, Ames. Dept. of engineering extension. [from old catalog] · Ames, Iowa, Engineering extension department, Iowa state college · leaf 59
h-blue. If an unexposed piece of fresh paper is washedthis coating is removed, leaving only the white paper; while a pieceproperly exposed to the light will turn a deep blue when similarlytreated. In blueprinting a tracing, the opaque ink lines protect the coat-ing underneath from the action of the… … , Felt Pad Blue PrintPaper - GlassTracing Fig. 78.—A printing frame. blueprint paper against the tracing. The back of the printing frameis then locked in position to hold the tracing and the paper firmly incontact, and the glass side of the frame exposed to sunlight from one-half minute to several…
Mechanical drawing
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