Blueprint Standards 3
While modern advances in replication technology have allowed other techniques to replace the tra-
ditional blueprint, some businesses continue to maintain this process. In most cases the diazo process
(which is an environmentally friendly process) has been replaced by xerographic print processes simi-
lar to standard copy-machine technology using toner on bond paper.
Plain-Paper Copies.
This process uses plain-paper machines; prints can be made from opaque originals, whereas diazos re-
quire translucent originals. Plain-paper copiers are mainly used in offices where changes and modifica-
tions are needed during the development stages or where the originals need to be put on vellum or film,
from which volume prints are made for distribution using the less expensive diazo process. This method
is especially useful in printing CAD plots done on bond paper (Figure 1.2). Plain-paper copiers are also
effective in making copies from shop-worn originals onto durable polyester film or vellum media. Some
copiers can also enlarge or reduce the size of the original drawing.
Photocopy Process.
The photocopy process is gaining extensive use for copying engineering and architectural drawings.
With this method a picture of the original drawing is used to then produce as many prints as required,
similar to a Xerox or other copying machines. This type of copier also has the added advantage of mak-
ing reductions or enlargements of the original drawing. These copy machines in fact very much resem-
ble the copiers found in the traditional office environment. The main difference is the capacity to copy
large drawings. The increasing popularity of these machines is due mainly to the use of ordinary paper
that does not require coating and avoids the possible hazards of ammonia.
Photographic Reproduction.
Various types of photographic reproduction are available that provide greater accuracy and detail, mak-
ing them easier to read, correct, and reprint. Photostats can be made from an original drawing by using
a large, specially designed camera that produces enlargements or reductions from the original work.
This direct print process delivers a negative with white lines and a dark background. A number of high-
quality reproduction methods such as microfilming are available that use a film negative made from the
original drawing. Projection prints from a photographic negative can be reproduced on matte paper,
glossy paper, vellum, and Mylar (Cronoflex™). These excellent-quality prints can be enlarged or re-
duced in scale with accuracy and are very durable.
To microfilm a drawing, one must first convert the original drawing to a microfilm frame using a spe-
cial microfilm-processing camera mounted on a frame over a platform. The camera reduces the draw-
ing in order to fit on the microfilm; the reduction can be varied by changing the height of the camera
above the drawing. After the film is developed, the negative is typically mounted on a standard-size aper-
ture or data card and is systematically filed for future retrieval. A microfilm-enlarger reader-printer with a
display screen is normally used to review the images as well as reproduce print copies of various sizes
from the negative. Microfilming is also an excellent means of storing drawings, thus eliminating the need
to retain cumbersome original tracings (Figure 1.3).