blueline
n.
A proof copy of a printed work made directly from the negatives that will be used to create the printing plates.
A reproduction of an architectural or engineering drawing made with blue lines on a neutral background.
Notes
Originally bluelines1, 2 were made using the diazo process and appeared as a blue-and-white positive. The term has been generalized to a variety of processes that produce bluelines on a neutral background. - Bluelines1 are a final check to verify camera work, folding, or trimming. - Bluelines2 are a positive image, maintaining the same polarity as the original drawing, as distinguished from blueprints, which are negatives.
