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§2. Materials

Lecture



To carry out various types of drawings in pencil, ink, paints apply drawing paper of mark O (regular) and B (top quality). A distinctive feature of the highest quality paper is the presence of watermarks visible on the light. Ordinary paper is available in two types: No. 1 — of higher quality and No. 2 — less dense and stiff.

For tracing works for the purpose of reproducing drawings by the method of blue-screening, transparent tracing paper is used, made on a paper or plain basis, and for paperless reproduction of drawings, tracing paper is used. Graphic paper is used to carry out draft images on a scale, various computational and graphic works, and white written checkered paper, usually with a cell size of 5x5, is used for sketching works.

Drawings made using graphic machines and photographs are made on sheet or roll drawing paper, photographic paper of various types or special paper made according to individual requirements.

Drawing pencils are marked by the hardness of the rods from 2T to 2M. The pencil lead is harder, the larger the number stands in front of the letter T, and the softer the larger the number stands in front of the letter M. Pencils with a medium-hard lead are designated as TM. On foreign-made pencils you can find the letter H instead of the letter T, and the letter M instead of the letter M.

For a certain type of graphic works apply the appropriate brand of pencil for hardness. So, to carry out the drawing in thin lines, pencils of the mark T, 21 are used, for the stroke of the drawing - the mark M, TM, for the execution of the pictures - mark M, 2М. Sharpen pencils on a cone or "spatula" for a length of up to 25 mm. At the same time, the graphite rod should protrude 7–9 mm from the wooden frame. Sharpening pencils better lead with sandpaper.

Some types of drawings on paper, as well as drawings on tracing paper (such drawings are simply called tracing paper) for blueprint are done with ink. It is usually produced in bottles and varies in quality and color. Most drawings are done in black ink. In the period of work the ink in the bottles must be protected from drying out. Thickened mascara is diluted with boiled water or ammonia. The quality of the lines drawn by the ink depends on the degree of its dilution, therefore, diluting the ink, it is necessary to control the quality of the lines.

Drawing gum are used in two types: to erase lines made with a pencil, and to erase lines made with ink. The rubber used for working with a pencil is soft and, when erasing, removes only particles of graphite from the paper without causing significant damage to it; the gum used for erasing carcasses contains hard additives and polishes the top layer of paper when erasing.

To obtain color images on the drawings apply watercolors, consisting of a thin coloring matter and binders. They are bred on water. The peculiarity of these paints is that when they are applied in layers one on another and when mixed, you can get the necessary shades. Sometimes they use glue paints and gouache, which is diluted in water. But they are not transparent and when applying one layer of paint to another top layer completely hides the bottom one.


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Descriptive Geometry and Engineering Graphics

Terms: Descriptive Geometry and Engineering Graphics