DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.25888#0104
ENGINEER AND MACHINIST’S DRAWING-BOOK.
paper will present, when thoroughly dry, a clean smooth
surface, not only agreeable to work upon, but also in the
best possible condition to take the colour.
The size of the brushes to be used will, of course, de-
pend upon the scale to which the drawing is made. Long
thin brushes, however, should be avoided. Those possess-
ing corpulent bodies and fine points are to be preferred,
as they retain a greater quantity of colour, and are more
manageable.
During the process of laying on a flat tint, if the sur-
face be large,—though this is seldom the case in drawings
of machinery,—the drawing may be slightly inclined,
and the brush well charged with colour, so that the edge
of the tint may be kept in a moist state until the whole
surface is covered. In tinting a small surface the brush
should never have much colour in it, for, if it have, the
surface will unavoidably present coarse rugged edges, and
a coarse uneven appearance throughout. A moderate
quantity of colour in the brush, well, though expeditiously,
rubbed into the paper, is the only method of giving an
even close-grained aspect to the surface. In fact, for
mechanical drawings, there is rarely occasion for well
charging the brush with colour. The tint in the brush
may be very dark or very light, but there should seldom
be much of it.
As an invariable rule let it be remembered, that no tint,
shade, or shadow, is to be passed over or touched until it
is quite dry.
In the examples of shading, which are given in this
work, it may be observed that all objects with curved
outlines have a certain amount of reflected light imparted
to them. It is true that all bodies, whatever may be their
form, are affected by reflected light; but, with a few ex-
ceptions, this light is only appreciable on curved surfaces.
The judicious degree and treatment of this light is of con-
siderable importance for the acquirement of an effective
style of shading.
All bodies in the light reflect on those objects which
surround them more or less light according to the situation.
Wherever light extends, reflection follows. If an object
be isolated, it is still reached, by reflected light, from the
ground on which it rests, or from the air which surrounds it.
In proportion to the degree of polish, or brightness in
the colour of a body, is the amount of reflected light which
it spreads over adjacent objects, and also its own suscep-
tibility of illumination under the reflection from other
bodies. A polished steam-cylinder, or a white porcelain
vase, receives and imparts more reflected light than a
rough casting or a stone pitcher.
Shade, even the most inconsiderable, ought never to
extend to the outline of any smooth circular body. On a
polished sphere, for instance, the shade should be delicately
softened off just before it meets the circumference, and
when the shading is completed the body colour intended
for the sphere may be carried on to its outline. This will
give a transparency to that part of the sphere influenced
by reflected light, which it could not have possessed if the
shade tint had been extended to its circumference. Very
little shade should be suffered to reach the outlines even
of rough circular bodies, lest the colouring look harsh, and
present a coarse appearance quite at variance with its
natural aspect. Shadows also become lighter as they
recede from the bodies which cast them, owing to the in-
creasing amount of reflection which falls on them from
surrounding objects.
Shadows appear to increase in depth as their distance
from the spectator diminishes. In nature this increase
is only appreciable at considerable distances. Even on
extensive buildings inequalities in the depth of the shadows
are hardly perceptible; much less, then, can any natural
gradation present itself in the shadows on a machine,
which, supposing it to be of the largest construction, is
confined to a comparatively small space. It is most im-
portant, however, for the effective representation of ma-
chinery, that the variation in the distance of each part of
a machine from the spectator should at once strike the
eye; and an exaggeration in expressing the varying
depths of the shadows is one means of effecting that object.
The shadows on the nearest and most prominent parts of
a machine should be made as dark as colour can render
them; the colourist being thus enabled to exhibit a marked
difference in the shadows on the other parts of the machine
as they recede from the eye. The same direction is ap-
plicable in reference to shades. The shade on a cylinder,
for instance, situated near the spectator, ought to be darker
than on one more remote; in fact, the gradation of depth
for the shades follows that which depicts the shadows.
As a general rule, the colour on a machine, no matter what
it may be intended to represent, should become lighter as
the parts on which it is placed recede from the eye.
Plate 57 presents some very good examples of finished
shading. The remarks which we now propose to offer
upon each of these figures are applicable alike to all forms
of a similar character.
Fig. 1 represents a hexagonal prism surmounted by a
fillet. The most noticeable part of this figure is the shadow
of the prism in the plan view. It presents a good example
of the graduated expression which should be given to all
shadows cast upon plain surfaces. Its two extremities
are remarkably different in their tone. As the shadow
nears the prism it increases rapidly in depth; on the con-
trary, as it approaches the other end it assumes a com-
paratively light appearance. This difference is doubtlessly
a great exaggeration upon what it would naturally dis-
play. Any modification of it, however, in the represen-
tation, would destroy the best effect of the shadow.
The direction which the shades and shadows take in
all the plans of the figures in this plate, is from the left
hand lower corner. This is rigorously correct, supposing
the objects to remain stationary, whilst the spectator views
them in both a vertical and a horizontal position. Never-
theless, to many, this upward direction given to the
shadows has an awkward appearance, and, perhaps, in the
plan of an entire machine, the shadows may look better
if their direction coincide with that which is given to
them in the elevation. If, however, the shadows be cor-
paper will present, when thoroughly dry, a clean smooth
surface, not only agreeable to work upon, but also in the
best possible condition to take the colour.
The size of the brushes to be used will, of course, de-
pend upon the scale to which the drawing is made. Long
thin brushes, however, should be avoided. Those possess-
ing corpulent bodies and fine points are to be preferred,
as they retain a greater quantity of colour, and are more
manageable.
During the process of laying on a flat tint, if the sur-
face be large,—though this is seldom the case in drawings
of machinery,—the drawing may be slightly inclined,
and the brush well charged with colour, so that the edge
of the tint may be kept in a moist state until the whole
surface is covered. In tinting a small surface the brush
should never have much colour in it, for, if it have, the
surface will unavoidably present coarse rugged edges, and
a coarse uneven appearance throughout. A moderate
quantity of colour in the brush, well, though expeditiously,
rubbed into the paper, is the only method of giving an
even close-grained aspect to the surface. In fact, for
mechanical drawings, there is rarely occasion for well
charging the brush with colour. The tint in the brush
may be very dark or very light, but there should seldom
be much of it.
As an invariable rule let it be remembered, that no tint,
shade, or shadow, is to be passed over or touched until it
is quite dry.
In the examples of shading, which are given in this
work, it may be observed that all objects with curved
outlines have a certain amount of reflected light imparted
to them. It is true that all bodies, whatever may be their
form, are affected by reflected light; but, with a few ex-
ceptions, this light is only appreciable on curved surfaces.
The judicious degree and treatment of this light is of con-
siderable importance for the acquirement of an effective
style of shading.
All bodies in the light reflect on those objects which
surround them more or less light according to the situation.
Wherever light extends, reflection follows. If an object
be isolated, it is still reached, by reflected light, from the
ground on which it rests, or from the air which surrounds it.
In proportion to the degree of polish, or brightness in
the colour of a body, is the amount of reflected light which
it spreads over adjacent objects, and also its own suscep-
tibility of illumination under the reflection from other
bodies. A polished steam-cylinder, or a white porcelain
vase, receives and imparts more reflected light than a
rough casting or a stone pitcher.
Shade, even the most inconsiderable, ought never to
extend to the outline of any smooth circular body. On a
polished sphere, for instance, the shade should be delicately
softened off just before it meets the circumference, and
when the shading is completed the body colour intended
for the sphere may be carried on to its outline. This will
give a transparency to that part of the sphere influenced
by reflected light, which it could not have possessed if the
shade tint had been extended to its circumference. Very
little shade should be suffered to reach the outlines even
of rough circular bodies, lest the colouring look harsh, and
present a coarse appearance quite at variance with its
natural aspect. Shadows also become lighter as they
recede from the bodies which cast them, owing to the in-
creasing amount of reflection which falls on them from
surrounding objects.
Shadows appear to increase in depth as their distance
from the spectator diminishes. In nature this increase
is only appreciable at considerable distances. Even on
extensive buildings inequalities in the depth of the shadows
are hardly perceptible; much less, then, can any natural
gradation present itself in the shadows on a machine,
which, supposing it to be of the largest construction, is
confined to a comparatively small space. It is most im-
portant, however, for the effective representation of ma-
chinery, that the variation in the distance of each part of
a machine from the spectator should at once strike the
eye; and an exaggeration in expressing the varying
depths of the shadows is one means of effecting that object.
The shadows on the nearest and most prominent parts of
a machine should be made as dark as colour can render
them; the colourist being thus enabled to exhibit a marked
difference in the shadows on the other parts of the machine
as they recede from the eye. The same direction is ap-
plicable in reference to shades. The shade on a cylinder,
for instance, situated near the spectator, ought to be darker
than on one more remote; in fact, the gradation of depth
for the shades follows that which depicts the shadows.
As a general rule, the colour on a machine, no matter what
it may be intended to represent, should become lighter as
the parts on which it is placed recede from the eye.
Plate 57 presents some very good examples of finished
shading. The remarks which we now propose to offer
upon each of these figures are applicable alike to all forms
of a similar character.
Fig. 1 represents a hexagonal prism surmounted by a
fillet. The most noticeable part of this figure is the shadow
of the prism in the plan view. It presents a good example
of the graduated expression which should be given to all
shadows cast upon plain surfaces. Its two extremities
are remarkably different in their tone. As the shadow
nears the prism it increases rapidly in depth; on the con-
trary, as it approaches the other end it assumes a com-
paratively light appearance. This difference is doubtlessly
a great exaggeration upon what it would naturally dis-
play. Any modification of it, however, in the represen-
tation, would destroy the best effect of the shadow.
The direction which the shades and shadows take in
all the plans of the figures in this plate, is from the left
hand lower corner. This is rigorously correct, supposing
the objects to remain stationary, whilst the spectator views
them in both a vertical and a horizontal position. Never-
theless, to many, this upward direction given to the
shadows has an awkward appearance, and, perhaps, in the
plan of an entire machine, the shadows may look better
if their direction coincide with that which is given to
them in the elevation. If, however, the shadows be cor-