Armengaud, Jacques Eugène; Leblanc, César Nicolas   [Hrsg.]; Armengaud, Jacques Eugène   [Hrsg.]; Armengaud, Charles   [Hrsg.]
The engineer and machinist's drawing-book: a complete course of instruction for the practical engineer: comprising linear drawing - projections - eccentric curves - the various forms of gearing - reciprocating machinery - sketching and drawing from the machine - projection of shadows - tinting and colouring - and perspective. Illustrated by numerous engravings on wood and steel. Including select details, and complete machines. Forming a progressive series of lessons in drawing, and examples of approved construction — Glasgow, 1855

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MANIPULATION OF SHADING AND SHADOWS.

95

the faint tint used on this occasion spread with the brush
lightly over the whole of that part of the rod situated on
either side of this line, thus blending into smooth rotun-
dity the graduated strips of tint drawn by the pen.

We shall conclude our exposition of mechanical colour-
ing by giving an example, wherein the various directions
for shading and for imparting numerous effects to the
appearance of coloured mechanical drawings, hitherto but
rarely practised, may be seen in combination.

An illustration of this kind is furnished by Plates lxiv.
and lxv., representing the elevation of a double blowing
engine. It is true that the art of engraving or of litho-
graphy has not achieved, and probably never will achieve,
all the effects which skilful colouring can produce; still
there may be observed in the Plates referred to most of
the prominent features pertaining to the above-described
style of shading. To one important direction there exem-
plified we would call especial attention, because the subject
of no other plate has been suited to express it; the gradual
diminution in the depth of shades and tints generally as
the distances in the positions of objects with reference to
the spectator increases. The cylinders, as being parts of
the engine situated nearest to the eye, receive the greatest
amount of depth in their shading and tinting. Beyond
the cylinders the fly-wheel, as a conspicuous part, next
arrests the attention. On this object we observe the tint
sensibly modified; for were the difference in depth less
obvious, a disagreeable harshness and a closeness of posi-
tion would be experienced, which could not fail to destroy
the harmony of the whole representation. Passing over
the fly-wheel, the eye rests upon the small entablature and
columns, parts which occupy the most remote situations
in the picture, and on which the effect of distance is ren-
dered much more apparent. The tint on the intermediate
parts partakes also, in a properly graduated measure, of
this means for indicating the locality of the different
members of the engine.

It is often advantageous, and sometimes necessary, in
mechanical drawings to show the manner of supporting
large or heavy machines. Sometimes the workshop or
other locality wherein a machine is placed requires repre-
senting. We shall, therefore, in order to render complete
our instructions for colouring machinery, indicate the
colours for depicting the materials ordinarily employed in
connection with constructions of so ponderous a nature.
As, however, such parts of a mechanical drawing are
almost invariably of very subordinate consideration, we
shall not treat of them minutely, our object being merely

to represent these unimportant additions in such a man-
ner that they may not impair the effect of the principal
subject of the picture.

Wood, stone, and brick are commonly used for the pur-
poses we have mentioned. The elevation of wood, sup-
posing it to be of a light colour, fir, for instance, may be
tinted with burnt umber; if it be of a dark character, as
oak, a little sepia should be added to the umber. A mix-
ture of Indian-red and Indian ink is well adapted for
shading wood, and for the shadows which fall on it. The
best representative of stone is a very light tint of Indian
ink. For the shading and shadows Indian ink is also
preferable. On some occasions, however, a very small
quantity of Indian-red, associated with the Indian ink,
will impart a pleasing effect to the shade or shadow.

The tint for brick-work must be varied to suit the
colour of the bricks used. For the elevation of ordinary
red brick-work, gamboge and burnt sienna, with more or
less of crimson-lake in proportion to the degree of red-
ness which the bricks present, is a very appropriate mix-
ture. Indian ink and Indian-red compound a tint well
suited for the shades and shadows, and a light tint of pure
lake exhibits the section of brick-work most naturally.

As leather is mostly used for the straps which connect
pulleys, cones, &c., it claims a passing notice. Warm
sepia answers very well for its body colour, and Indian
ink and Indian-red for the shades and shadows.

Illustrations of wood, stone, brick, and leather, may
be seen on Plate lxiv.

For machinery we have recommended darkness in the
colouring; we do not object even if it present a certain
degree of “heaviness" in its appearance, seeing that the
preponderating components of every large machine are
dark and heavy. On the contrary, in representing the
materials we are now speaking of, care should be taken
to express the shades and shadows, as well as the body
colours, very lightly, for two reasons; firstly, because the
natural aspects of these materials are light, and therefore
ought not, in their representations, to be overloaded with
colour ; and secondly, because in all mechanical drawings
they occupy the position of mere adjuncts, indicating
foundations or localities, and consequently should not be
conspicuously expressed, but kept subdued and light. A
striking representation of machinery being the object
aimed at, nothing should be allowed to distract the atten-
tion from a consideration of the important parts of the
drawing, which alone require to be brought prominently
forward and exhibited to the best advantage.
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