SECTION 11
The quality and often the complexity of a map or graphic is dependent on the nature of the original artwork. Photographic reduction and high contrast photography can improve the quality of linework on reproductions although most flaws and all errors will still remain.
Basically artwork can be prepared in positive or negative formats, or in a combination of the two. The reproduction method chosen, the economics of the situation and the availability of equipment and materials dictate the format utilized. Both positive and negative artwork are normally produced as colour-separated plates, overlays or components. This requires a pin registration system so that the images on the various overlays retain their correct relationship when a composite negative or positive of the overlays is made. This also demands the use of stable-base materials, as artwork produced on unstable materials will shrink or expand with variations in temperature and humidity. Thus stable, polyester-based, plastic films are a requirement for all graphics which are not simple, single colour designs produced on one overlay. These plastic films are also more permanent and of consistent quality. Erasures and changes can be made relatively easily. For these reasons tracing papers, art papers and similar materials are not used in most mapping operations except for minor projects, internal planning or display work.
The following general guidelines and work habits should be followed for the production of artwork:
i) The accuracy of the final product is dependent on the accuracy of the original manuscript and the accuracy of the subsequent drawing or scribing;
ii) Cleanliness is vital. The following work habits should be followed:
a) Hands should be clean at all times. Many people use linen or cotton gloves to avoid staining the artwork;
b) All instruments such as scales, triangles, straight edges, etc., should be cleaned regularly;
c) The work table should be cleaned before use. All work should be covered when not in use, as well as the overlays not currently being worked on. On complex pen and ink work, only the small area currently being drawn should be uncovered;
iii) The work area should be kept clear of clutter. When not in use, opened bottles should not be left on desks to avoid spillage;
iv) A good source of even lighting is necessary for cartographic work; it should provide a high level of illumination without glare or strong shadows.
Until recently, positive artwork such as the pen and ink drawing was the only method of producing original artwork. It remains a common procedure for short run, illustrative and relatively quickly produced graphics with which much of this manual is concerned. Normally, traditional drafting techniques using modern graphic aids are used for producing positive artwork. Automated plotting devices and other forms of computer technology can also produce positive artwork.
Positive artwork is associated with the following reproductive processes:
i) Artwork produced on translucent material at the intended reproduction scale can be used to produce a negative or positive copy by the contact method in a vacuum frame. It can also be used for direct reproduction by a positive working contact method such as diazo;
ii) Artwork produced on opaque (white) material at the desired final scale can be viewed directly and optically reproduced by a process camera, xerography, etc. The total effect of any revision made to the artwork can be seen immediately;
iii) Artwork produced at a larger scale than that intended for reproduction can be optically reduced by a process camera. Graphic symbols and complex details are easier to construct at a larger scale. Reduction sharpens the image, removes small irregularities and generally improves registration of the overlays. The reduced size of lines, symbols and lettering must be considered when drafting the original artwork.
This is a flexible method of producing artwork, using a wide range of materials, inks, pens and equipment:
The following factors should be considered when selecting drafting materials:
i) Costs : Material costs are usually a minor part of the total cost of cartographic products; using the appropriate material, however, can usually save a great deal of time in this labour intensive field. To minimize costs, expensive stable-based materials should not be used when their characteristics are not required;
ii) Dimensional stability: Temperature and humidity variations cause shrinking and stretching of all paper-based products. All image separated graphics should be drawn on stable-base polyester films. As the size of the graphic increases so should the thickness (and stability) of the drafting material;
iii) Tooth: This is the technical term given to the slightly roughened surface of polyester plastic films to ensure ink will adhere to the surface, creating a good image. A smooth surface will not accept ink; a rough surface will provide a poor image and wear out drawing instruments;
iv) Translucence: Translucence is the state of transmitting light without being transparent. This dictates the ease with which you can see through the drafting material on a light table. Vital for tracing purposes, translucence also eases the comparison of separated layers of a graphic;
v) Erasability: Changes are often necessary on original artwork. The drafting material should permit erasure several times without damaging, smearing or ghosting;
vi) Strength: Drafting material should withstand a great deal of wear and handling;
vii) Absorbency: Drafting materials should not be absorbent. Paints and inks contain a great deal of liquids. Any material which absorbs these liquids will distort, curl and tear easily.
In cartography, coloured inks are used only to produce display products. The colours in maps and graphics which will be reproduced by the printing process are drawn with black, high density inks (refer to Section 12).
A wide range of black drafting inks is produced by such manufacturers as Pelikan, Koh-l-Noor, Higgins, etc. Temperature and humidity variations cause changes in the flow characteristics of all inks. It is unlikely that a single product will suffice for all drawing instruments and conditions which are encountered in a drafting office. Thus it is advisable to experiment with the various types available to determine their suitability. A new ink product from Koh-l-Noor uses a latex base instead of the usual lacquer base. This not only produces a dense black image but also minimizes the clogging of technical pens. All inks have a finite shelf life.
Technical pens have become the most widely used drawing instruments. They can be used both freehand or with a mechanical guide. Their ease of use and the consistency of the linework are the major reasons for their popularity.
The ink, contained in a reservoir, supplies a round replaceable drawing point via a feed mechanism. Each line width requires a different size pen point, hence a wide range of point sizes is available. Normal steel points wear out rapidly when used on plastic drafting materials; more durable jewel points are available for this purpose at a higher cost. Tungsten carbide points are also available but are most suitable for use with plotting machines. All pens will clog if left opened or filled for long periods of time without regular cleaning. The quality of linework is reasonable for most purposes although lines tend to be grey unless an opaque ink is used.
Technical fountain-type pens such as Pelikan Graphos have replaceable nibs for each specific line width. The pen nibs are made of a mild steel and thus wear out rapidly when used on plastic drafting materials. These pens are best suited for straight line work using a straight edge, making them ideal for borders, neat lines, etc. The quality of linework is superior to that of technical pens. The cleaning and changing of pen nibs, however, is a messy process.
Ruling pens have been largely replaced by technical pens. They still are the most versatile and economical drawing instruments available as individual pens are adjustable and thus capable of producing varying line widths. They can be re-sharpened when worn so a quality instrument can last for years. Considerable effort is required, however, to learn how to use these pens. They can produce a dense, high quality line but need to be continually refilled and cleaned.
A contour pen is essentially a ruling pen with a swivel handle. Unlike the ruling pen it is primarily used freehand, especially for drawing contours and other isolines. It is the drawing instrument which produces the smoothest freehand curves but considerable practice is required to master its use.
Quill pens (crowquill pens, dip pens, straight pens) consist of flexible metal nibs mounted in wooden or plastic handles. These are the least expensive drawing instruments available. Replaceable nibs should be obtained in a variety of sizes and stiffness. Quill pens are the only pens which allow the drawing of lines of varying widths from a single nib.
The following good quality equipment is required to produce professional products:
| i) | The most basic item required is a sturdy, flat drafting table sized to accommodate the largest maps which will be produced. A light table which contains an adequate illumination source is also required. Access to both a drafting table and a light table is ideal although many cartographers work exclusively on light tables; |
| ii) | T squares are used for horizontal alignment and drawing straight lines. They can only be properly used if one side of the drafting table is perfectly straight and rigid; |
| iii) | Steel straightedges are useful for drawing straight lines. They should not be used as a cutting edge to avoid damage caused by a slipped knife blade; |
| iv) | Parallel rules consist of straightedges which are attached to the drawing board by guide wires, and are useful for drawing straight lines and general layout work; |
| v) | Rolling rules are short straightedges with a wheel insert that keeps them straight. They are an excellent aid as they can be moved easily about the drawing; |
| vi) | Drafting machines consist of two scales or straightedges at right angles that can be rotated through 90° by a control device similar to a protractor. Widely used in engineering drafting, they are useful for plotting angular measurements, drawing straight lines and as a base for lettering guides; |
| vii) | Line-up tables consist of a light table with two moveable guide arms mounted at right angles to each other. They are a precise layout tool; |
| viii) | Drafting triangles made either of acrylic or of steel are aids for angular plotting and for use as short straightedges; |
| ix) | French curves are indispensable aids for drawing smooth curved lines and a variety of curved shapes; |
| x) | Ships curves are precisely engineered curves which are useful for precision curved work of all types. Railroad curves are similar to ships curves; |
| xi) | Spline curves are flexible curves used for drawing long smooth projection curves. They consist of a flexible plastic spline and heavy hooked lead weights which keep the spline smoothly curving through pre-determined points; |
| xii) | Beam compasses are large radius compasses often necessary for drawing large circles, arcs, etc.; |
| xiii) | Proportional dividers are useful for the mechanical changing of scales (refer to Section 7); |
| xiv) | Spacing dividers have eleven points hinged together like an accordian. They are used to divide a line into any number of equal parts from two to ten. They are useful for dividing bar scales, plotting coordinate positions, etc.; |
| xv) | Swivel knives are used for cutting irregular shapes on pre-printed patterns sheets, masks, shading films, etc. |
Text may be produced by any of the methods listed in Table 11.1. It may be used directly on artwork or photographically reproduced onto photographic paper, stripping film, image transfer or sticky-back materials for use on overlays. These positive overlays can also be photographed or contacted in a vacuum frame to component negatives for use in the production of composite negatives. A precision grid, which consists of a clear polyester film base having an image of fine, closely and evenly spaced horizontal and vertical lines, may be used to align the text or lettering on the map or graphic.
A wide variety of symbols can be produced by any of the methods listed for producing text (refer to Table 11.1 and Figure 11.1). Photographic reproduction of any of these symbol sources can greatly increase the size range of available symbols. They can be photographically reproduced onto such materials as stripping film, image transfer, diffusion transfer (sticky-backs) or photographic paper in a variety of sizes for use on overlays. Hand-drawn symbols should be drawn larger than required and then photographically reduced to sharpen the image.
| METHOD | ADVANTAGES | DISADVANTAGES |
|---|---|---|
| Hand Lettering | Least complex system. Very economical. No special equipment or materials necessary Flexible. Curved and spaced names are easily laid out. Can produce very small sizes. | Needs considerable skill and practice to achieve professional results. Non-standardized results. Few styles achievable. |
| Template (e.g., Wrico-Uno) | Simple. Minimal skills necessary. Uniform letters. Equipment is inexpensive. | Spacing and alignment difficult. Limited styles available. Shapes often unattractive. Small sizes not available. Curves hard to control. Slow. |
| Pantograph - Small (e.g., Leroy) | Long life equipment. Skills easily learned. Good spacing easily attained. Attractive standardized letters. Good selection of sizes in small to mid range. Widely available. Height/slant control scriber gives variations of styles. | Relatively slow. Many templates needed for a range of lettering. Non standard styles are expensive. Hard to produce curved lettering. Poor for headline or display use. |
| Pantograph - Larger (e.g., Varigraph) | Basic set produces wide range of styles. Excellent for display or title work. Single template can produce many variations of sizes and slanted letters. Long life equipment. Relatively Inexpensive. | Small sizes not available. Cumbersome for detail work. Basically used for headlines. Slow. |
| Dry-Transfer | Wide range of styles, sizes and colours available. High quality. Highly uniform. No special equipment needed. Clean and dry. Curved and spaced names are easily laid out. | Expensive to maintain a “useful supply”.Products have shelf life. Slow. Standardized sheets are wasteful. |
| Typewriter (e.g., Varityper, IBM Composer) | Relatively inexpensive and quick. Several styles available. | High quality paper needed. Only limited variation in sizes available. |
| Photo type composition | Fastest method. High quality. Requires few manual skills. Uniform spacing. Wide range of sizes and styles available. Names can be easily moved. Excellent for blocks of text. | Expensive equipment. Equipment needs regular maintenance and servicing. Photographic reproduction material costly (strip- ping or sticky-back film). Darkroom needed. |
Figure 11.1 Examples of preprinted pattern, area and point symbols. (After J. Campbell, 1984)
(Patterns, Tones): Pattern and area symbols are available in two basic forms: the pressure-sensitive, rub-down variety and a more commonly used cut-out type (Figure 11.1). In the latter kind the required area of the pattern or tone is cut out with a swivel knife. The portion required is removed from its backing sheet, placed into position on the artwork, trimmed to the exact shape and then burnished into place. There is a wide variety of patterns available in lines, dots, and other shapes.
As a general rule, finely textured patterns must be selected so that small areas on the map receive enough elements of the pattern to make them easily recognizable. Screen tints should not be finer than 120 lines per inch to avoid problems in reproduction. Similarly, if a tone is required, tints that are coarser than 75 lines per inch are generally seen as patterns and not tones and should be avoided unless the artwork is photographically reduced.
Preprinted cut-out solid colour and pattern materials are useful for displays and artwork prepared for slides or optical colour separation. If photomechanically reproduced, red colour material can be used wherever an area of solid black is needed. Using red material instead of black is easier, as the former is actinically opaque but visually transparent, allowing the underlying artwork to be viewed.
The major problems in the use of cut-out area patterns or colours are cleanliness and smooth burnishing. The adhesive backing of these materials will easily pick up dirt such as lint or hairs. Air bubbles and areas of weak adhesion will show up distinctly on many reproductions, as will smearing and ghosting. Care must be taken when cutting the adhesive film over inked lines on a drawing. The knife blade may easily damage the linework and trimmed excess material may also remove part of the image when it is stripped off. The tone of identical tints will vary from sheet to sheet, making it difficult to maintain even tones in large areas. Many commercial products have a grey or thin black image, rather than a dense black one, which is difficult to reproduce photomechanically. It is a relatively slow process to cut out complex shapes. A few of the manufacturers of cut-out area symbols include Artype, Letratone, Zip-a-Tone, Para-Tone, etc.
It is difficult to obtain precise, quality and permanent images by pen and ink drawing, i.e. positive artwork. The level of manual skill required for excellent positive artwork is high and it takes a considerable period of time for even talented people to develop consistent abilities. In contrast, negative artwork is more easily prepared and less skill is required to produce quality products.
This process is used extensively in modern map production; it produces directly the equivalent of a line photographic image. Accurate, sharp and consistent lines can be produced by a person with relatively little experience. Scribed linework is produced more quickly, easily and cheaply than drafted linework. Scribing produces high contrast negative artwork which eliminates a considerable amount of photomechanical processing. Scribing is also normally produced at the reproduction scale, avoiding the need for photographic reductions so common in positive artwork.
Scribing film consists of a clear base of dimensionally stable polyester, covered by an actinically opaque or translucent scribable coating. Examples of scribing film include Scribe Coat produced by Keuffel and Esser Company and Scribe Base produced by Kimoto USA Inc. Some scribing films are available with a pre-sensitized coating to which the base map or worksheet is exposed in a vacuum frame to provide a guide image (refer to Section 5.1.4.4) for scribing. These coatings are often diazo sensitized and must be developed in ammonia fumes. Others have a photographic emulsion. These scribing films are relatively expensive and have a short shelf life. Refer to Table 11.2 for a description of various scribing film types.
A guide image can also be simply reproduced by wiping a diazo or bichromate solution on regular scribing film at any desired stage of production. Diazo images are positive acting and require positive worksheets if positive guide images are needed. In contrast, bichromates are negative acting and require negative worksheets if positive guide images are required. Both types of solutions are available in several colours so a multi-coloured guide image can be achieved by successive applications and exposures.
An alternate and relatively economical method of scribing is to produce the entire image wrong-reading or reversed (refer to Figure 12.1). When photomechanically contacted, emulsion to emulsion, this will produce the required right-reading image on the printing plate directly. Manufacturers such as Keuffel and Esser Company produced reversed lettering transplates for this purpose.
| COLOUR TYPE | USAGE | COMMENTS | CHARACTERISTICS |
|---|---|---|---|
| Rust | On a light table. | Most common variety. | Excellent actinic opacity (impervious to photographic light). |
| Green | On a light table. | Easiest colour on the eyes. | Good actinic opacity. |
| Yellow | On a light table. | 2nd easiest colour on the eyes. | Excellent actinic opacity. |
| Red | Light table may not be necessary. Trace scribing. | Translucent, guide image not necessary. | Excellent actinic opacity. |
| (White on green or white on rust) | Automated plotters. No light table required. | Scribed linework is highly visible. | Double coated. |
| Scribe n ' Peel | Scribing linework and producing open-window negatives. | Film useful for two separate applications. | Excellent actinic opacity. Scribe layer over transparent peelable layer. |
| Duplication Scribing Film | Revision work. | Diazo sensitized. | Good opacity. |
| Contone | Continuous-tone and line combination products. | Both contact and projection speed reproduction. | Photographic emulsion on scribing film. Reproduces air photos. White and rust surface. |
A wide range of scribing tools is available, some of which are shown in Figure 11.2. Generally scribing points or needles are mounted in a tripod support perpendicular to the scribed surface. Some tools use sharpened blades rather than points. As the scriber (tripod) is moved across the scribing film using a small amount of vertical pressure, the needle, point or blade penetrates the coating and scrapes it away from the transparent base. Too much pressure, will gouge the underlying polyester base resulting in a poor photographic image. Corrections and revisions are simple to make using an opaque substance specifically formulated for this purpose although rescribing may be difficult.
The scribing process removes part of the coating as loose particles. This debris is actinically opaque and if left on the film will cause gaps in lines and broken images; it will transfer to any contact frame or other material with which it is in contact. It is also highly abrasive and can rapidly wear out or seize up the ball feet of scribing tools. Most debris can be removed by frequent brushing with a soft bristle brush or by wiping with a damp cloth or tissue. The sticky side of drafting tape or tacky gum erasers may also be used for removing the loose particles. All linework must be checked frequently under a magnifier for traces of loose particles.
Points are available in various diameters ranging from 0.05 mm (.002 inch) upwards in regular increments; above a certain size they are chisel shaped to facilitate cutting the wider lines. Points are also available for scribing double lines, triple lines and combinations of thick and thin lines to represent road casings, special symbols, borders, etc.
Scribing tools are available in both freehand and rigid versions, the latter for use with a straightedge or french curves. There are also special scribers available for scribing dots, buildings, etc., as well as a wide variety of templates used for scribing symbols. Manufacturers of these tools include Roto Instruments, Keuffel and Esser, and Astrascribe.
The shape of scribe points and their associated advantages and disadvantages may be described as follows:
| Type | Advantages | Disadvantages |
|---|---|---|
| Round | Can be used freehand. Easy to set up. Can be used in rigid or swivel head scribing tool. | Pressure needed increases with point size. Should not be used for square symbols. |
| Conical | Can be used freehand. Easy to set up. Can be used in rigid or swivel head scriber. | Needs rigid holder to keep tip perpendicular. Pressure needed increases with size. Should not be used for square symbols. |
| Chisel (point or blade) | Removes scribing film coating cleanly. Wide range of sizes and styles available. | Needs careful alignment and setting up. Needs swivel head scriber. |
There are three primary materials used to construct scribe points: steel, sapphire and tungsten. Tungsten points are expensive, very hard and long wearing; they cannot be resharpened. Steel points are the cheapest and withstand rough handling; they tend to wear out quickly but can be resharpened. Jewel points (sapphire) are expensive, brittle and fragile and cannot be resharpened. They are, however, long lasting if handled with care.
Open-window negatives for area symbols can be prepared by using cut and peel techniques on strip masking or peelable materials such as Amberlith or Rubylith by Ulano Corporation or Kimoto Strip Coat by Kimoto USA Inc. They can also be produced photomechanically by an etch and peel process using sensitized peelable materials which consist of a thin ruby-coloured film coating on a transparent polyester plastic base. These materials are exposed in registration with a line negative of the boundary lines in a vacuum frame under high intensity ultraviolet light.
The peelable material is then developed and subsequently etched by a separate chemical process. Any unwanted boundary line can be masked by the use of an opaque formulated for that purpose. The desired open areas are peeled with tweezers or similar sharp instruments. A corner is carefully lifted and the rest of the area stripped off. If an opaque line remains at the edge of the open area this can be removed by swabbing with a moist material.
Sensitized peelable materials can be processed in normal room lighting. Patterns and tonal values can be added to a map by using contact screens or screen tints on the open-window negatives. Examples of sensitized peelable material include Peel Coat produced by Keuffel and Esser Company and Etch n' Peel produced by kimoto USA Inc.
A mask is an area of opaque material on a clear overlay which prevents light from striking and therefore exposing an area on a negative or positive during the photomechanical process. Masks can be made by painting or opaqueing the area on a sheet of transparent plastic. They can also be hand cut on masking material which consists of a transparent polyester base coated with an actinically opaque thin film coating which is peelable such as Rubylith. The coating is normally transparent, allowing the artwork which requires masking to be viewed. Masks can also be produced by the photomechanical etch and peel process described in Section 11.1.2.3.
Occasionally a coloured graphic is required both quickly and economically, e.g., for internal usage within an organization or to illustrate a topic at a meeting. There are many simple and economical colour systems available to produce artwork for such graphics. Each system described may be used to produced multi-coloured artwork. If many colour copies are required the “artwork” can be optically colour separated for printing on an offset press.
Coloured pencils are the quickest and cheapest colour system. Normally considered unsuitable for reproduction they may be adequate for internal use.
The main problem in the use of coloured pencils is inconsistent colour. A great deal of streaking is normally evident in the most careful artwork. This can be largely overcome by means of the stomping technique. A stomp is a pencil-like device composed entirely of compressed paper with tapered ends. The tip of the stomp is moistened with ordinary lighter fluid and then rubbed gently over the coloured areas. It will soften and smoothen the coloured areas removing streaks and brightening the image. Lighter fluid, however, is flammable and should be used with care. Stomps are available from graphic arts suppliers. An example of stomping is shown in case study #5, Geology of the Island of Newfoundland, shown in Section 13.
These relatively inexpensive and convenient products are available in a wide variety of colours, tip widths and tip styles. When the markers are not in use, it is important to keep the caps on to prevent the solvents from evaporating, thus drying the markers.
Applying colour on large areas without obvious streaking is difficult. The use of a good quality art board is important as marker solvents easily penetrate inferior materials, such as diazo paper, resulting in colour bleeding or spreading. Plastics, having non-porous surfaces, have the opposite problem. The colour sits on the surface and is easily smeared. The use of an acrylic art spray prior to colouring the surface, however, can prevent this problem.
Adhesive-backed coloured acetate film in both vivid and pastel hues can be applied to either side of both positive or negative transparencies. Similarly opaque paper artwork can be given vibrant colours by applying adhesive-backed colour tapes and symbols.
The area is cut out with a sharp knife and burnished into place on the artwork after necessary trimming has been carried out. Care must be taken to apply the colour correctly as the adhesive or colour may be damaged by repositioning.
The use of these films is slow but excellent results can be achieved on displays and artwork intended for photographic reproduction, e.g., overhead transparencies, slides, etc. Because they are easily damaged they are not suitable for diazo reproduction, long term usage or highly complex work.
This versatile instrument is one of the most common and valuable tools used by commercial artists. The airbrush is a precision, penlike spraying device approximately the size of a fountain pen. It is connected by a hose to a controllable air supply which forces light-bodied ink, liquid colours or paint from a small reservoir cup or bottle. The air supply is normally obtained from a small, portable electric air compressor. For casual usage, however, small bottles of compressed air can be economically obtained. Airbrushes are available in a wide range of prices and performance capabilities. The more expensive models are capable of spraying extremely fine jets of colour in small areas. The cheaper versions are useful for applying broad areas of colour or tone.
Airbrushes can apply precise amounts of tone or colour to almost any surface, whether opaque or transparent. They are superior in this regard to virtually any pen, brush or marker. Shading and blending of colours can be done with ease, making airbrushes particularly valuable for hill shading, hypsometric colouring, depth illumination, etc. Edges must be carefully masked to prevent colour from accidentally being added to the wrong area. Special “fisket” solutions are available to crate paintable masks which are easily removed.
The aerosol container, with its fine spray, approximates the effects of an airbrush, though the amount of control is relatively limited. Most of the colours available are bright. Professional-looking graphics can be obtained on transparent or opaque materials. As in airbrushing, smooth edges can be created by masking the unwanted area with an adhesive mask.
A simple and effective mask can be created with rubber cement, suitably thinned, which is peeled off after the aerosol has been applied.
Figure 11.2 Examples of scribing tools: (a) rigid scriber and (b) swivel scriber, both of which are used for linework; (c) pentype scriber used for freehand work. (After A.H. Robinson et al., 1984)
