The pad may be made as follows: 1 part of white glue to 5 parts by weight of glycerine. Soak the glue over night, in just enough water to cover it. Bring to the boiling point slowly, without burning; then add the glycerine, and thoroughly mix. Pour into a shallow pan; remove all air-bubbles from the surface with a stiff card; and allow to cool. Before using each time, wash thoroughly with a sponge and allow to dry partially before applying the drawing; also wash well immediately after using, to remove all traces of ink.
The proportions may be varied slightly for different climates. A cold climate will require more glycerine, and a warm climate more glue. The pad should be stiff enough to resist pressure from the fingers when firmly pressed upon it.
Other additional ingredients are sometimes used. Perhaps they have their advantages; but the mixture as described has been used very suc cessfully. Often, in very hot weather, after a pad is made, it may seem too soft to work well. In such a case, placing the pan on a cake of ice will harden the mixture and make it satisfac tory.
A cheaper pad may be made by using a mix ture of a special clay and glycerine. While not giving so many prints as the glue pad, it can be used more economically for large drawings. Hectograph pencils may be had in many colors, which are used for making full-size details. These drawings are copied in the same way as the regular pen-and-ink drawings.
The hectograph process is gradually gaining in favor, and in some localities it is used exten sively. It has several features to commend it: (1) All materials can be represented in appropriate colors.
(2) Copies are very cheap, and can be made on paper or prepared cloth.
(3) The draftsman finds it convenient when making revisions, as parts of the drawing can be cut out and a correct portion inserted. No matter how badly the drawing is cut and patched, the prints are perfect.
(4) In assembling different drawings on a sheet, they may be shifted at will, and a better arrangement secured.
(5) When a sheet is composed of small drawings, the draftsman may work over the small drawings more com fortably than if compelled to work on a large sheet.
The hectograph process, however, has some drawbacks, which may be indicated as follows: (1) Small details cannot be shown so clearly, as the lines must be quite heavy if a number of prints are required.
(2) The drawings fade more or less if exposed to a. bright light, but they are permanent enough for most work.
(3) Some draftsmen do not like to use the inks, as they are sticky and soil the fingers. This, however, should apply only to the inexperienced.
Hectograph inks may be purchased of dealers everywhere, in all colors. Below are suggested colors for various sections of materials: Purple—For lines in general, outlines, profiles, etc.; also for sections of plaster, aiad concrete.
Red—For dimension lines, and for sections of brick work.
Blue—For iron, steel, flashing, etc., in section. Brown—For sections of terra-cotta.
Green—For sections of stone or marble.
Yellow—For wood.
For the blue-print process, the drawing to be reproduced is preferably done on tracing cloth, on the rough side, in black ink. Erasures may be made on this, and the work corrected; but the finished drawing has to be complete in every respect, as every line is reproduced just as drawn.
For the hectograph process, we shall need to make the lines much heavier, and may use colored inks. Mistakes cannot be erased, but are cut out, and a new piece of paper placed over the hole, and the drawing continued.
Tracing cloth makes the most satisfactory material all around for the original drawing. It is translucent or semi-transparent, will make good prints by almost any process, and is much more desirable than paper for filing away and for constant use in the drafting room.
The use of colored inks is not to be recom mended. They make the tracing look very pretty, but they print very poorly, some shades of green being hardly visible on the blue-print. Red reproduces very faintly, and when this color is used for dimension lines they should be heavy. Black is the most serviceable color to use. In steel detailing, the entire drawing is done in black—even dimension lines.