While to finish a drawing without any error or defect should be the draughtsman's object, he should never be in haste to reject a damaged drawing, but should exercise his ingenuity to see how far injuries done to it may be remedied. Never lose a drawing once begun; and since prevention is easier and better than cure, always work calmly, inspect all instruments, hands, and sleeves, that may touch a drawing, before commencing an operation; let the paper, instruments, and person be kept clean, and when considerable time is to be spent upon a portion of the paper, let the remainder be covered with waste paper, pasted to one edge of the board. For the final cleaning of the drawing, stale bread, or the old-fashioned black indiarubber, if not sticky, is good; but, aside from the carelessness of ever allowing a drawing to get very dirty, any fine drawing will be injured, more or less, by any means of removing a considerable quantity of dirt from it. Another excellent means of preventing injuries, which should be adopted when the drawing is worked upon only at intervals, is to enclose the board, when not in use, in a bag of enamelled cloth or other fine material.

Colours

For colouring drawings, the most soluble, brilliant, and transparent water-colours are used; this particularly applies to plans and sections. The colour is not so much intended to represent that of the material to be used in the construction, as to clearly distinguish one material from another employed on the same work. The following table shows the colours most employed by the profession: -

Carmine or Crimson Lake

For brickwork in plan or section to be executed.

Prussian Blue........

Flintwork, lead, or parts of brickwork to be removed by alterations.

Venetian Red........

Brickwork in elevation.

Violet Carmine....

Granite.

Raw Sienna...........

English timber (not oak).

Burnt Sienna.......

Oak, teak.

Indian Yellow........

Fir timber.

Indian Red.........

Mahogany.

Sepia.........

Concrete works, stone.

Burnt Umber ........

Clay, earth.

Payne's Grey........

Cast iron, rough wrought iron.

Dark Cadmium.......

Gun metal.

Gamboge.........

Brass.

Indigo ...........

Wrought iron (bright).

Indigo, with a little Lake

Steel (bright).

Hooker's Green........

Meadow land.

Cobalt Blue ..........

Sky effects.

And some few others occasionally for special purposes.

In colouring plans of estates, the colours that appear natural are mostly adopted, which may be produced by combining the above. Elevations and perspective drawings are also represented in natural colours, the primitive colours being mixed and varied by the judgment of the draughtsman, who, to produce the best effects, must be in some degree an artist.

Care should be taken in making an elaborate drawing, which is to receive colour, that the hand at no time rest upon the surface of the paper, as it is found to leave a greasiness difficult to remove. A piece of paper placed under the hand, and if the square is not very clean, under that also, will prevent this. Should the colours from any cause, work greasily, a little prepared ox-gall may be dissolved in the water with which the colours are mixed, and will cause them to work freely.