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7-10-2015, 12:12

DRAWING MATERIALS A. Film

There are several types of drawing surfaces, e. g., transparent, semitransparent, and opaque. Most drawing suppliers will have sample catalogs of the range of drawing surfaces, so that it is possible to make a selection to suit a particular need and a particular budget. The transparent and semitransparent surfaces usually have a plastic base (polyester or acetate) and are referred to as film. There are several types available. Plastic drawing film is usually available in a variety of thicknesses and in a transparent (clear), single-sided, semi-matte or double-sided, semi-matte finish. The transparent film is useful for drawing details of objects that can be traced through the film. Thus, copying from photographs or tracing ship’s timbers are examples where detail needs to be seen through the drawing surface and maximum clarity is therefore required. With this shiny, clear plastic, the surfaces have to be kept clean and free of grease. The type of pen and ink selected must give an even, dense line which takes well to the surface. Alcohol-based, fiber-tipped pens seem to work best on this drawing material.



The matte or semi-transparent materials are excellent for line drawings and illustrations. Ink mistakes can be repeatedly scraped off using a scalpel or a damp rubber. Care should be exercised not to damage the surface excessively, as this can cause the ink to run along fine scratches. The material is dimensionally stable and, most important, completely waterproof. This is often essential when working in the field, as drawings often get wet or can be splashed or affected by extremes of humidity and dampness.



There are, however, some important disadvantages attached to using matte or semi-transparent film. The surface is prone to pick up grease, particularly from the illustrator’s hands. When drawing, it is necessary to keep hands scrupulously clean and it is preferable to work with one’s hand on a paper tissue. If grease gets onto the surface from a thumbprint, for example, the ink takes differently to the surface, causing uneven lines. It is, therefore, essential to prepare the surface prior to inking by treating it with inking powder. Also, plastic surfaces are not as porous as other surfaces and there is a tendency for the lines to fade; thus, if the pen is giving an uneven flow, the line density varies from thick black to a gray where the surface shows through. This creates formidable problems when photographing the drawing for reproduction. Also, where the lines or ink surfaces are thick, the ink tends to be shiny causing reflection problems in photography. Plastic film takes a long time to dry, particularly in high humidity conditions. Thus, very great care must be taken not to smudge wet lines, and ink lines must be totally dry before pencil construction lines can be erased. A hair dryer can be useful to speed the drying process. Finally, plastic is a very expensive drawing material, but its use is strongly recommended for all permanent recording work.



Other tracing papers include the cheap tracing papers of the greaseproof paper type. They take India ink extremely well, but are not dimensionally stable, and are particularly affected by humidity. In the latter case, if they get wet, a valuable drawing that has taken many hours to produce can be ruined. As it is very cheap, about one quarter the price of plastic film at the time of this writing, it is ideal for producing preliminary drawings and tentative construction plans.



B. Paper



White cartridge paper is often used for drawings and has the advantage that the ink takes well on it. The main objection is that corrections are difficult, particularly as either the paper is damaged if the ink is removed, or the porosity of the surface is altered if a white opaque covering paint is used. Drawing paper comes in a variety of grades of loading, so that those with the greatest loading have the smoothest surface. It is necessary to use care in the selection of paper. The rougher paper allows inks to run whereas paper with a lot of surface additives causes pens to clog and gives rough lines. Bristol board has an excellent surface for line drawings. There are also white plastic drawing papers made from the same materials as the drawing film. These have some of the inherent problems of film, but are extremely strong and robust.



Some very effective artifact drawings have been published using white scraper board (Kaijser, 1981). The scraper board is a card with a special surface, usually black, which when scraped with a needle or scalpel reveals a white surface. It is possible to either use a white scraper board and scrape to reveal the black, or to use a plain white surface, block the object in India ink, and then scrape this to reveal the white below. Drawings made on scraper board can have interesting surface effects which can make the material of the object, glass bottles, for example, look particularly realistic.



Graph paper usually comes in blocks of A4 or larger formats or in rolls 750 mm to 1m wide in a variety of lengths. It can be opaque or transparent and is available in a variety of colors. However, graph paper, particularly in roll form, can be inaccurate; for example, one particular grade was oversized by +0.15% longitudinal and +0.25% in the lateral direction. One useful aspect of colored graph paper is that with a judicial choice of colors, film, and filter, it is possible to photograph an object drawn on graph paper so that the lines do not show. Thus the grid can be used as a reference when making the drawing and it is possible to dispense with mechanical drawing aids.



C. Inks



Most drawing ink manufacturers provide inks for various uses. The type of ink selected will depend on the type of pen and the type of surface to be used. It is helpful to remember that certain inks are compatible with particular pens, and mixing different inks in the pen reservoir should be avoided. In particular, etching inks can dissolve parts of certain types of pens.



D. Pens



There is an immense variety of pens for drawing purposes. They may be divided into four categories each of which is described next.



1. Dip Pens



Dip pens are used for simple artwork. Usually, they are obtained either with italic, straight-cut nibs to give different thicknesses to different parts of the letter (like Roman typeface or italic handwriting). The also come with nibs with a disk end which give lineal letters with equal thickness throughout, although the ends of letters are round-ended not square.



2. Stilo Pens



Stilo pens are produced by a number of different companies. In general, these are based on a holder with a screw-in pen tip and ink reservoir. The pen tip consists of a hollow tube with a flat end. The ink flows from the reservoir down the fine tube to the flat surface at the end of the nib. When the pen is drawn on the surface of the paper, the ink flows out across the flat nib surface giving a line equal in thickness to the tip diameter. The tips range from 0.13 to about 2.0 mm (in the DIN system the double increments are 0.18, 0.25, 0.35, 0.5, 0.7,1.0, 1.4, and 2.0mm). Down the center of the tube is a fine wire, the upper end of which is attached to a little cylindrical weight. This acts to control the flow of ink and to help unblock the pen when it clogs. Thus, by shaking the pen back and forth, or screwing the cap on and tapping the end on a table, the weight moves the wire similarly backward and forward, helping to clear the tube.



The tips of some types of stilo pens are made of very hard material. This type of pen is essential for working on plastic drawing film which is very abrasive. Ordinary pens, when used on film, only last a short time before the tip is worn away to the shoulder, causing an increase of about 0.5 mm in line thickness and producing very messy lines. The tips of most stilo pens are manufactured with a shoulder so that when using a straightedge, the ink is not drawn under the surface of a ruler causing blotting. The shoulder or bevel on the tip should always be kept clean (paper tissue can be used to clean the tip), as ink, dirt, and film debris tends to accumulate around the bevel, especially when drawing straight lines. This accumulation often causes the line to thicken and can cause the ink to run under the ruler, which is just what it is designed not to do. These pens are compatible with a range of stencils, so that various styles of lettering can be made for each pen size (see Section VI).



One of the most serious problems with stilo pens is that they seem doomed to clog. A variety of methods of humidification and air-tight holders have been devised, but if the pens are left open for any length of time they block up. To unblock the pen, I have found that there are two alternative methods:



1.  Ignore the manufacturer’s instructions and take the pen apart, extract the little weight with the fine wire, and clean the pen out. Then try to put the fine wire back into the pen, which you will not be able to do without breaking it and ruining the pen, exactly as the manufacturer said it would. Then buy a new pen at great cost and inconvenience to yourself. In reality, it is possible to remove the wire if it is 0.7 mm or thicker, but it is usually not possible to get anything smaller back into the pen.



2.  Get a small glass jar with a lid, or buy the more expensive cleaning unit recommended by the manufacturer, fill it with warm water and a bit of washing-up liquid. Take the cap and the cap insert apart and wash in warm, running water to remove superficial ink (use a toothbrush if necessary), then pop the cap and all the parts into the jar (this is really worthwhile as a caked cap will cause the pen to dry out more quickly). Take the reservoir off the pen, empty the ink out, and wash it. Take apart what you are allowed to take apart according to the instructions, wash and place in the jar. In particular, most pens have a complicated air passageway between nib and holder which allows air, but not ink, to pass up to the reservoir, thus relieving the pressure caused by the ink flowing out. This should be carefully scrubbed with a toothbrush to ensure the passageways are clear. You can often tell when this breather is blocked, because as the pen is held, the warmth of your hand causes the ink to be forced out of the tip and drip over your almost complete artwork. Leave everything in the jar for several days, preferably a week, change water from time to time, and thoroughly wash out under a water faucet each time. This is really the only way for the very fine pens. There are some ingenious aerosol pen cleaning kits in which the nib screws into the can and the cleaning fluid is forced through the nib.



3.  Fiber Pens



A number of excellent fiber-tipped pens are now available. It is important with these pens to test if the ink is really waterproof. This can be done by drawing a few lines on paper and film and then wetting the surface (giving a reasonable few seconds to dry). If the ink runs, then the pen should not be used, even for general writing. For example, if a field register is left out in the rain and the ink runs, a lot of very important information may be lost. The felt or fiber-tipped pens are available in a variety of tip shapes which can be quite useful, particularly, when drawing a plan or object at very large scale prior to reduction (see Section VI about reduction). There are also a number of fiber pens with nibs encased in a metal tube that give a constant line thickness of 0.2 and 0.4 mm, although the ink is a little thin.



4.  Other Pens



With the gradually improving inks, ballpoint pens are coming back into vogue. They are a great improvement on the greasy, uneven lines that were produced when the Biro first came out. Some of the better quality pens can be used for artwork.



E. Pencils



There are many different types of pencils for different types of drawing, ranging from soft to hard. It should be noted that, because plastic drafting film is exceedingly abrasive, there are special problems when using pencil on it. Hard pencils (8H), when used on film, tend to produce thick lines like a soft pencil (4B) would on paper. To produce a light, fine line pencil work on film should be as light as possible with a hard pencil; if too much pressure is exerted it will scratch the surface. There are also pencils (F)



Available especially for use on film. When working on film, the pencil point will need to be constantly sharpened as it wears down; a piece of fine emery paper is ideal for this. Clutch pencils are also useful, particularly because some have an easy-to-use sharpening tool attached to their end. A useful alternative are fine propelling pencils with leads of 0.3- and 0.5-mm diameter which are held in a push-click button pencil holder. Thus, leads are continually used up, but the line thickness is constant. The various hardness of the leads makes very little difference on film, although it is a different story on paper, where it is best to select a medium-grade pencil for fine-point lead. An 8H pencil will scratch a paper surface as well as leaving a fine line, making it difficult to erase. Using a sharp HB softly on paper gives clear lines that can be easily erased.



IV. DRAWING EQUIPMENT A. Drawing Box



One of the most useful items for a person who does a lot of drawing work in a variety of places (home, work, expeditions, visits to other collections, etc.) is a drawing box (Figure 11.3).This holds all the basic equipment


DRAWING MATERIALS A. Film

Figure 11.3 A standard drawing box showing the range of equipment generally required for artifact and general site plan drawings.



For any type of drawing. From personal experience, it is amazing how often departmental or group equipment is either missing, broken, or unusable when it is needed for a vital, rushed job, whereas with one’s own equipment there is only one person that can be blamed if it is not there. In general, you know exactly what you have, and that it is all in one place. But beware, there will be constant harassment by people wanting to borrow pens that are always in working order. The following is what the author keeps in a drawing box:



• A3 drawing board with parallel rule, rotating head; in this case, a Rotring Rapid, but others are just as good and some possibly cheaper 50 sheets of pre-cut A3 drawing film and some A3 metric graph paper 1 set of 9 drawing pens 0.13-2.0 mm, Rotring Sec-o-mat Isograph “F” pens



Compass set, small circles, large circles, and compass beam radii up to about 250 mm



500-mm stainless steel flat ruler 10-m retractable tape measure Circular protractor, diameter 300 mm Set of large calipers, 500-mm jaws Set square



Vernier calipers, 250 mm Vernier depth gauge, 250 mm Programmable calculator



Set of scalpel blades and blade holders, emery board for sharpening blades, and some backed razor blades Scale rules (1:2,1:4,1:2.5,1:5,1:7.5)



Set of stencils for Isograph pens Fine-point pencils and leads (0.2 and 0.5 mm)



Felt-tipped pens, various colors, tip shapes, and sizes Rubbers, ordinary for ink on film and rod rubbers and holders Various inks Profile devices Blue Tac and sticking tape Scissors Paint brushes



Proportional dividers and standard dividers Measuring devices



The small retractable steel tape is one of the most useful measuring devices. It is compact, flexible, and ideal for measuring large objects (about 10m maximum). Scale rules are used for drawing, particularly for working plans at fixed scales like 1:2, 1:4, 1:5, 1:10, 1:20, and 1:100. These, provided they are read correctly, simplify the drawing process; for example, 34.81m at a scale of 1:5 requires a division and then the use of a ruler, whereas a scale rule requires only the use of the rule.



Measuring the outside and inside diameter of objects ranging from ceramic pots to gun barrels can present some problems. Vernier calipers are useful for outside diameters and just inside the necks of tubes. Otherwise large double-arc calipers can be bought or made for use on outside and inside diameters, provided in the latter case you can extract the caliper without altering the reading. It is worth having mild steel calipers chromed to prevent rusting. This is particularly important if they are taken anywhere near the sea, otherwise without the chrome they rust very badly.



There are various ways of measuring in places where a direct measurement cannot be made. For example, it is not normally possible to measure the wall thickness inside a jar with conventional calipers because when the calipers are extracted, the separation changes. Home-made scissor - or X-calipers are one method that can be used in this situation (Figure 11.4). The point of separation on the bottom caliper is duplicated on the top, thus while the inaccessible bottom one is in the inside position the reading can be taken from the top. Alternatively, it is possible to utilize ordinary calipers with a small block placed against the outside surface of the vessel. The calipers measure the thickness of the wall of the object together with the block, the increased caliper jaw separation allows the calipers


DRAWING MATERIALS A. Film

Figure 11.4 X-calipers used to measure the wall thickness inside jars and pots. The calipers are set so that the gap is identical at each end of the caliper.



To be extracted without disturbing the setting. The thickness is then obtained quite simply by subtracting the block thickness from the overall measurement.



 

 

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