_THE PREPARATION AND USE OF THE INSTRUMENTS._
The points of drawing instruments require to be very accurately prepared
and shaped, to enable them to make clean, clear lines. The object is to
have the points as sharp as they can be made without cutting the paper,
and the curves as even and regular as possible.
[Illustration: Fig. 17.]
[Illustration: Fig. 18.]
The lining pen should be formed as in Figure 17, which presents an edge
and a front view of the points. The inside faces should be flat across,
and slightly curved in their lengths, as shown. If this curve is too
great, as shown exaggerated in Figure 18, the body of the ink lies too
near the point and is apt to flow too freely, running over the pen-point
and making a thick, ragged line. On the other hand, if the inside faces,
between which the ink lies, are too parallel and narrow near the points,
the ink dries in the pen, and renders a too frequent cleaning necessary.
Looking at the face of the pen as at A in Figure 17, its point should
have an even curve, as shown, the edge being as sharp as it can be made
without cutting the drawing paper. Upon this quality depends the
fineness and cleanness of the lines it will make. This thin edge should
extend around the curve as far as the dotted line, so that it will be
practicable to slant the pen in either of the directions shown in Figure
19; and it is obvious that its thickness must be equal around the arc,
so that the same thickness of line will be drawn whether the pen be held
vertical or slanted in either direction.
[Illustration: Fig. 19.]
[Illustration: Fig. 20.]
The outside faces of the pen should be slightly curved, so that when
held vertically, as in Figure 20 (the dotted line representing the
centre of the length of the instrument), and against the square blade S,
the point will meet the paper a short distance from the lower edge of S
as shown. By this means it is not necessary to adjust the square edge
exactly coincident with the line, but a little way from it. This is an
advantage for two reasons: first, the trouble of setting the square-edge
exactly coincident is avoided, and, secondly, the liability of the ink
to adhere to the edge of the square-blade and flow on to the paper and
make a thick, ragged line, is prevented.
The square being set as near to the line as desired, the handle may be
held at such an angle that the pen-point will just meet the line when
sloped either as in Figure 21 or 22. If, however, the slope be too much
in the direction shown in Figure 21, practice is necessary to enable the
drawing of straight lines if they be long ones, because any variation in
the angle of the instrument to the paper obviously vitiates the
straightness of the line. If, on the other hand, the square be too close
to the line, and the pen therefore requires to be sloped as in Figure
22, the ink flowing from the pen-point is apt to adhere to the
square-edge, and the result will be a ragged, thick line, as shown in
Figure 23.
[Illustration: Fig. 21.]
[Illustration: Fig. 22.]
[Illustration: Fig. 23.]
[Illustration: Fig. 24.]
[Illustration: Fig. 25.]
[Illustration: Fig. 26.]
Each of the legs should be of equal thickness at the pen-point edge, so
that when closed together the point will be in the middle of the edge.
The width and curve of each individual point should be quite equal, and
the easiest method of attaining this end is as follows:
Take a small slip of Arkansas oil-stone, and with the pen-points closed
firmly by the screw trim the pen-edges to the required curve as shown at
A, Figure 17, making the curve as even as possible. Then stone the faces
until this curve is brought up to a sharp edge at the point between the
two pen-legs forming the point.
Next take a piece of 000 French emery paper, lay it upon some flat body
like the blade of a square, and smooth the curve of the edge enough to
take off the fine, sharp edge left by the oil-stone; then apply the
outside flat faces of the pen to the emery paper again, bringing the
pen-edge up sharp.
The emery paper will simply have smoothed and polished the surfaces,
still leaving them too sharp, so sharp as to cut the paper, and to take
off this sharp edge (which must first be done on the inside faces) open
the pen-points as wide as the screw will permit. Then wrap one thickness
of the emery paper upon a thin blade, as upon a drawing-triangle, and
pass the open pen-points over it, and move the instrument endwise,
taking care to keep the inside face level with the surface of the emery
paper, so that the pen-points shall not cut through. Next close the
pen-points with the screw until they nearly, but not quite, touch, and
sweep the edge of the pen-point along the emery paper under a slight
pressure, so moving the handle that at each stroke the whole length
around the curved end of the pen will meet the emery surface. During
this motion the inside faces of the pen-point must be held as nearly
vertical as possible, so as to keep the two halves of the pen-point
equal.
The pen is now ready for use, and will draw a fine and clean line.
It is not usual to employ emery paper for the purpose indicated, but it
will be found very desirable, since it leaves a smoother surface and
edge than the oil-stone alone.
Circle-pens are more difficult to put in order than the straight-line
pen, especially those for drawing the smallest circles, which cannot be
well drawn unless the pen is of the precise right shape and in the best
condition.
A circle-pen is shown in Figure 24, in which A represents the point-leg
and B the pen-leg. The point-leg must be the longest because it requires
to enter the drawing paper before the pen meets the surface. The point
should be sharp and round, for any edges or angles on it will cause it
to widen the hole in the paper when it is rotated. To shape the points
to prevent the enlargement of the centre in the paper is one of the most
important considerations in the use of this instrument, especially when
several circles require to be drawn from the same centre. To accomplish
this end the inside of the point-leg should be, as near as possible,
parallel to the length of the instrument (which is denoted in Figure 24
by the dotted line) when the legs are closed, as in the figure. If the
point is at an angle, as shown in Figure 25, it is obvious that rotating
it will enlarge the top of the centre in the drawing paper. The point
should be sharp and smooth on its circumferential surface, and so much
longer than the pen-point that it will have sufficient hold in the paper
when the instrument stands vertical and the pen-point meets the surface
of it, which amount is about 1/64th of an inch.
We may now consider the shape of the pen-point. Its inside surfaces
should be flat across and to the curve shown in Figure 24, not as shown
exaggerated in Figure 25, because in the latter the body of the ink will
be too near the pen-point, and but little can be placed in it without
causing it sometimes to flow over the edges and down the outside of the
pen.
A form of pen-point recently introduced is shaped as in Figure 26, the
object being to have a thin stream of ink near the marking pen-point and
the main body of the ink near at hand, instead of extending up the pen,
as would be the case with Figure 24. The advantage thus gained is that
the ink lies in a more solid body, and having less area of surface
exposed to the air will not dry so quickly in the pen; but this is more
than offset by the liability of the ink to flow over the crook at A, and
cause the pen to draw a thick ragged line. The pen-point must be
slightly inclined toward the needle-point, to the end that they may
approach each other close enough for drawing very small circles, but it
should also stand as nearly vertical as will permit that end to be
attained. As this pen is for drawing small circles only, it does not
require much ink, and hence may be somewhat close together, as in Figure
24; this has the advantage that the point is not hidden from
observation.
In forming the pen-point the greatest refinement is necessary to enable
the drawing of very small true circles, say 1/16th of an inch, or less,
in diameter. The requirements are that the pen-point shall meet the
surface of the paper when the needle-point has entered it sufficiently
to give the necessary support, and that the instrument shall stand
vertical, as shown by the dotted line in Figure 24. Also, that the pen
shall then touch the paper at a point only, this point being the apex of
a fine curve; that this curve be equal on each side of the point of
contact with the paper; that both halves forming the pen be of equal
thickness and width at the pointed curve; and that the point be as sharp
as possible without cutting the paper.
The best method of attaining these ends is as follows: On each side of
the pen make, with an oil-stone, a flat place, as C D, Figure 27 (where
the pen-point is shown magnified), thus bringing both halves to an edge
of exactly equal length, and leaving the point flat at D. These flat
places must be parallel to one another and to the joint between the two
halves of the pen. As the oil-stone may leave a slightly ragged edge, it
is a good plan to take a piece of 00 French emery paper, lay it on a
flat surface, and holding the instrument vertically remove the fine edge
D until it will not cut. Then with the oil-stone shape the curved edge
as in Figure 28, taking care that the curve no more than brings the flat
place D up to a true curve and leaves the edge sharp, with only the very
point touching the paper, which is represented in the cut by the
horizontal line.
[Illustration: Figures 27. 28. 29. 30. 31. 32.]
The point must have a sharp edge all around the curve, and the two
halves must be exactly equal in width, for if one half is wider than the
other, as in Figure 29 at a, or as in Figure 30 at b, it will be
impossible to draw a very small circle true. So, likewise, the two
halves of the pen must be of exactly equal length, and not one half
longer than the other, as in Figures 31 or 32, which would tend to cut
the paper, and also render the drawing of true small circles
impracticable.
When the pen is closed to draw a very small circle the two halves of the
pen-leg should have an equal degree of contact with the surface of the
paper, and then as the legs are opened out to draw larger circles the
contact of the outside half of the pen will have less contact with the
paper. The smaller the circle, the more difficult it is to keep the
point-leg from slipping out of the centre, and the more difficult it is
to draw a clear line and true circle; hence the points should be shaped
to the best advantage for drawing these small circles, by oil-stoning
the pen, as already described, and then finishing it as follows:
After the oil-stoning, open the two valves of the pen-leg wide enough to
admit a piece of 000 French emery paper wrapped once around a very thin
blade, and move the pen endwise as described for the straight-line pen.
This will smooth the inner surfaces and remove any fine wire-edge that
the oil-stone may leave. Close the two halves of the pen again, and
lightly emery-paper the outside faces, which will leave the edge sharp
enough to cut the paper. The removal of the sharp edge still left, to
the exact degree, requires great care. It may best be done by closing
the pen until its two halves very nearly, but not quite, touch, then
adjust it to mark a circle of about 3/16 inch diameter, and strike a
number of circles in different locations upon the surface of a piece of
0000 French emery paper.
In marking these circles, however, let the instrument stand out of the
perpendicular, and do very little while standing vertically. Indeed, it
is well to strike a number of half-circles, first from right to left and
then from left to right, and finally draw a full circle, sloping the pen
on one side, gradually raising it vertically, and finally sloping it to
the other side. This will insure that the pen has contact at its extreme
point, and leave that point fine and keen, but not enough so to cut the
paper. To test the pen, draw small circles with the pen rotated first in
one direction and then in the other, closing its points so as to mark a
fine line, which, if the pen is properly shaped, will be clear and fine,
while if improperly formed the circle drawn with the pen rotated in one
direction will not coincide with that drawn while rotating it in the
other. The same circle may be drawn over several times to make a
thorough test. If a drawing instrument will draw a fine line correctly,
it will be found to answer for thick lines which are more easily made.
In thus preparing the instruments, the operator will find that if he
occasionally holds the points in the right position with regard to the
light, he will be able to see plainly if the work is proceeding evenly
and equally, for if one-half of the pen is thicker at the point or edge
than the other, it will show a brighter line. This is especially the
case with instruments that have become dull by use, for in that case the
edges will be found quite bright, and any inequality of thickness shows
plainly.
[Illustration: Fig 33.]
[Illustration: Fig. 34.]
It follows, from what has been said, that the needle-point and pen-point
should stand vertical when in use, and to effect this the instruments,
except in the smallest sizes, are provided with joints, such as shown at
A and B in the bow-pencil or circle-pencil, in Figure 33. These joints
should be sufficiently stiff that they will not move too easily, and yet
will move rather than that the legs should sensibly spring without
moving at the joint. The needle-point leg should be adjusted by means of
the joint, to stand vertical, and the same remarks apply equally to the
pen-leg; but in the case of the pencil-leg it is the pencil itself and
not the leg that requires attention, the joint B being so adjusted that
the pencil either stands vertical, or, what is perhaps preferable, so
that it stands inclined slightly towards the needle-point. In
sharpening the pencil the inner face C may be made concave or at least
vertical and flat, and the outer convex or else bevelled and flat,
producing a fine and long edge rounded in its length of edge. In using
the circle-pencil and circle-pen it will be found more convenient to
rotate it in the direction of the arrow in Figure 34. It should be held
lightly to the paper, and the learner will find that he has a natural
tendency to hold it too firmly and press it too heavily, which is
_especially to be avoided_.
If in drawing a small circle the needle-point slips out of the paper, it
is because the pencil-point is too long; or, what is the same thing, the
needle-point does not protrude far enough out from the leg. Or if the
instrument requires to be leaned over too much to make the pencil or pen
mark, it is because the pen or pencil is not far enough out, and this
again may cause the needle-point to slip out of the paper.
[Illustration: Fig. 35.]
[Illustration: Fig. 36.]
In Figure 35 is shown a German instrument especially designed to avoid
this slipping. The peculiarity of this instrument consists in the
arrangement of the centre point, which remains stationary whilst the pen
or pencil, resting by its own weight on the paper, is guided round by
gently turning, without pressure, the small knob at the upper end of the
tube. By this means the misplacing or sliding of the centre-point and
the cutting of the paper by the pen are avoided. By means of this fixed
centre-point any number of concentric circles may be drawn, without
making a hole of very distinguishable size on the paper.
[Illustration: Fig 37.]
In applying the ink to the bow-pen as to all other instruments, care
must be taken that the ink lies between the points only and not on the
outside, for in the latter case the ink will flow down too freely and
make a broad, ragged line, perhaps getting on the edge of the square
blade or triangle, and causing a blot of ink on the drawing.
In using a straight line or lining pen with a T square it may be used as
in Figure 36, being nearly vertical, as shown, and moved from left to
right as denoted by the arrow, S representing the square blade. But in
using it, or a pencil, with a straight edge or a triangle unsupported by
the square blade, the latter should be steadied by letting the fingers
rest upon it while using the instrument, the operation being shown in
Figure 37. The position, Figure 36, is suitable for long lines, and that
in Figure 37 for small drawings, where the pen requires close adjustment
to the lines.