DRAFTING MEDIA - continued

types: paper, cloth, and film. For all practical purposes, you, as a SEABEE draftsman, will use tracing paper, profile paper, plan/profile paper, and cross-section paper. Although it is not found in the draftsman kit, illustration board is used for preparing signs and charts. Tracing cloth and film are rarely used by SEABEE draftsmen, and hence will not be described here. TRACING PAPER (also called TRACING VELLUM) is a high-grade white (or slightly tinted) transparent paper that takes pencil well, and from which pencil lines can be easily erased. Also, reproductions can be made directly from pencil drawings on tracing paper; however, for better results in reproduction, a pencil drawing on tracing paper is usually inked over. PROFILE, PLAN/PROFILE, and CROSS- SECTION PAPER are referred to as GRIDDED MEDIA. Each type of gridded media is designed for a specific purpose. Most gridded media used by EAs are suitable for reproduction. PROFILE PAPER is normally available in two grid patterns: 4 by 20 lines (4 lines vertical and 20 lines horizontal) per inch and 4 by 30 lines per inch with the vertical lines accented every 10th line. Horizontal lines on the 4 by 20 are accented medium-weight every 5th line and heavyweight every 50th line. Horizontal lines on the 4 by 30 have heavyweight accent lines every 25th line. Profile paper is generally used for road design profiles. PLAN/PROFILE PAPER has rulings and grid accents similar to those of 4 by 20 and 4 by 30 profile paper, except that the grid patterns oc- cupy only the lower half of the paper. The upper half is plain paper, used to draw the plan view in relation to the profile or to add explanatory notes to the profile. Plan/profile paper is also used for road design. CROSS-SECTION PAPER, sometimes re- ferred to as graph paper, is available in a variety of grid patterns. Generally, graph paper used by the EA has a grid scale of 10 by 10 lines per square inch. It is used for drawing road cross sections, rough design sketching, preparing schedules, plotting graphs, and many other uses. Most drafting media are available in three styles: plain sheets or rolls, preprinted sheets with borders and title blocks, and sheets with non-reproducible grids. For further information on the many varieties of drafting media available, refer to suppliers’ catalogs, such as those published by Keuffel & Esser Co. and Eugene Dietzgen Co. ILLUSTRATION BOARD is a drawing paper with a high rag content mounted on cardboard backing. The type normally found in a SEABEE drafting section has a smooth white drawing surface that takes ink readily. Normally, the board is 30 in. by 40 in. and comes in 50-sheet packages. Illustration board is used by the EA for making signs and for large unmounted charts and for mounting maps, photos, and drawings that require a strong backing. A thinner board, called BRISTOL BOARD, is also used for making small signs and charts. The thickness of bristol board is about the same thickness as an ordinary index card. Unlike illustration board, bristol board has two white smooth sides that take ink very well. Bristol board is less expensive than illustration board and is easily cut, to size with a paper trimmer. It is available in many sizes; the most popular size is 20 in. by 30 in. in 50- or 100-sheet packages. 142.131 Figure 2-1.—Grades of drafting pencils. 2-4