a. Plot the points that correspond to the known distances on the appropriate scales of the
b. Draw a straight line through these points, extending the line until it intersects the vertical
scale at the right.
c. The last point of intersection gives you the minimum height of the lettering in inches.
Make your letters as large as reasonably possible. Lacking the use of the nomograph, a good rule of
thumb is to use no lettering smaller than 14 point (approximately 3/16").
You may make your viewgraphs and overlays by hand, or you may make them using a
mechanical/chemical process, e.g., diazo.
a. Handmade Viewgraphs. The simplest form of viewgraph is a handmade projectional.
(1) You make the handmade viewgraphs by drawing or writing on a clear sheet of acetate
with a grease pencil or with a plastic marking pen. You can easily erase the acetate with a cloth to make
corrections and updates, or to reuse the plastic.
(2) Stabilo pencils work well for finely detailed drawings or copy. They work well on most
any type surface.
(3) Felt tip pens are useful for coloring small areas. Since the colors of these pens are
transparent, you must apply them carefully. Each overlapping stroke deepens the tone and may produce
(4) The use of standard drawing ink presents a problem. The clear acetate sheets are
smooth, and therefore do not absorb the ink. The practice of roughing up the surface of the plastic with
a fine abrasive (such as talcum powder or pumice) or an eraser enables the surface of the acetate to hold
the ink. Unfortunately, the use of abrasives scratches the surface of the acetate. These scratches appear
as dark marks on the screen. Using special acetate inks eliminates this problem.
(5) Since you do not normally mount these handmade transparencies, they are not very
durable. They tend to wrinkle, smudge, and tear. For more permanent products, you will want to
produce mechanically- or chemically-processed overlays.
b. Diazo Transparencies. The handmade method of preparing viewgraphs is fast and simple.
You use this method when time is