The base sheet and base map can be produced with a computer graphic program or drawn by hand. The decision as to which is best normally depends on the skill level of the design staff, available computer hardware and software, and budget. Hand-drawn base sheets and maps should be generated on vellum or Mylar. Vellum is a semitransparent paper used primarily when pencil is the chosen medium for drawing. Typical pencil grades are HB, H, and 2H. It is not recommended to draw with ink on vellum because it is difficult to erase. Vellum is generally cheaper than Mylar and slightly lighter in weight.
By comparison, Mylar or “drafting film” is a thin transparent plastic film used when either pencil or ink is the chosen medium for drawing. Extra care must be taken
Base sheet for the Duncan residence.
Base map for the Duncan residence.
when using pencil on Mylar because pencil tends to smear very easily on the plastic film. Pencil smears less on vellum than on Mylar because the lead of the pencil is embedded more in the texture (called tooth) of the vellum. Advantages of Mylar are that ink can be erased rather easily from it, and it is a little more durable than vellum because it is not as susceptible to tearing or wrinkling. However, the sturdiness of both vellum and Mylar enables numerous copies to be made from them. One caution: Refrain from using tracing paper to draw the base sheet or base map. Tracing paper is much too light and flimsy and, as a result, tears and rips easily.