Drawing-paper.—The names and sizes of the sheets of drawing paper are given in the following table:—
| Inches | |
| Demy | 20 × 15 |
| Medium | 22 × 17 |
| Royal | 24 × 19 |
| Imperial | 30 × 22 |
| Atlas | 34 × 26 |
| Double Elephant | 40 × 27 |
| Antiquarian | 52 × 31 |
The above sizes must not be taken as exact. In practice they will be found to vary in some cases as much as an inch.
Cartridge-paper is made in sheets of various sizes, and also in rolls.
Hand-made paper is the best, but it is expensive. Good cartridge-paper is quite suitable for ordinary drawings.
Centre Lines.—Drawings of most parts of machines will be found to be symmetrical about certain lines called centre lines. These lines should be drawn first with great care. On a pencil drawing centre lines should be thin continuous lines; in this book they are shown thus — - — - —.
After drawing the centre line of any part the dimensions of that part must be marked off from the centre line, so as to insure that it really is the centre line of that part: thus in making a drawing of a rivet, such as is shown at (a) fig. 1, after drawing the centre line, half the diameter of the rivet would be marked off on each side of that line, in order to determine the lines for the sides of the rivet.
Inking.—For inking in drawings the best Indian ink should be used, and not common writing ink. Common ink does not dry quick enough, and rapidly corrodes the drawing pens. The pen should be filled by means of a brush or a narrow strip of paper, and not by dipping the pen into the ink.
In cases where there are straight lines and arcs of circles touching one another ink in the arcs first, then the straight lines; in this way it is easier to hide the joints.
Colouring.—Camel's-hair or sable brushes should be used; the latter are the best, but are much more expensive than the former. The colour should be rubbed down in a dish, and the tint should be light. The mistake which a beginner invariably makes is in having the colour of too dark a tint.