Linear drawing and lettering for beginners

Preface

A faithful following of the directions given in this book will, it is hoped, furnish the student enough training in the use of drafting implements to enable him to construct accurate pencil drawings, make clean-cut ink lines, and do legible lettering.

The work embraced in Chapters II and III constitutes the course of fifty working hours in Linear Drawing and Lettering in Stanford University, as it has been given during the past eight years as preparation for the drafting in the courses in Descriptive Geometry, Elementary Machine Drawing, Surveying, and Graphic Statics.

I am indebted to Mr. C. B. Wing, Professor of Structural Engineering, and to Mr. G. H. Marx, Associate Professor of Mechanical Engineering, for many suggestions for this book.

J. C. L. FISH.

Palo Alto, California,

TABLE OF CONTENTS,

Chapter I.— Instruments And Materials

§ 1. Equipment.

Instruments and materials required, 1.

Drawing-board, 2-4.

T square, 5-7.

Triangle, 8-10.

Irregular or French curve, 11-13.

Drawing-paper and tracing-cloth," 14-16.

Pencil, 17-19.

Ruling-pen, 20-22.

Rubber pencil-eraser, 25.

Stale bread, 26.

Rubber ink-eraser, 27.

Steel ink-eraser, 28.

Pumice-powder, 29.

Divider, 33-35.

Compass, 36-38.

Compass lead, 39.

Compass pen, 40.

Bow instruments, 41-43.

Lettering-pen, 44-46.

Blotter, 47.

Chapter Ii.— A Course In Linear Drawing

§3. To Lay Out and To Finish a Plate. §6. Plate 3a : Circles.

To fix the paper, 48.

Cutting line, 49.

Border line, 50.

To finish a plate, 51.

Pencil circles, 58. Pen circles, 59.

§ 7. Plate 4: Accurate Construction.

§ 4. Plate 1 :

Medium Lines.

To construct the square, 60.

To divide a line into

Full lines, 52.

Dot-lines, 54.

To bisect an angle, 61.

parts, 62.

Dash-lines, 53.

Dash-dot-lines, 55.

To inscribe a circle, 61.

To ink Plate 4, 63.

§ 5. Plates

2 and 3.

§ 8. Plate 5 :

Irregular Curve.

Plate 2 : Heavy lines, 56.

Plate 3: Fine lines, 57.

To use the French curve, 64.

To construct Plate 5, 65.

equal

Chapter Iii.— A Course In Lettering

in Lettering. § 11. A'ertical and Inclined Lettering. Details of

§ t). Required Work

Materials for lettering, 66. Places o auu / ; orunary ibl-

Preliminary practice, 67. tering, 68.

Plates 8-17 : Titles, 69..

Final work on plates, 70.

§ 10. Vertical and Inclined Lettering. Introductory Remarks.

Directions of letter-stems and axes, 71. ■

Horizontal guides, I-guides, 72.

Individual pen-strokes, 73.

0 as a model for curve forms, 74.

Difference between Vertical and Inclined lettering, 75.

Letter widths, 76.

Letter- and word-spacing, 77.

Details of lower-case o, 78.

Details of c e s, 80.

Details of h m n r u, 81.

Details of f i j 1 1, 82.

Details of capitals O Q, 84.

Arrangement and proportions of the parts of a title, 90.

Details of C D G J S U, 85.

Details of E F H I L T, 87.

Details ofAKMNVWXY Z, 88.

Details of numerals and fractions, 89.

Common faults in titles made by beginners, 91.

To construct a title, 92.

§12. Titles.

Chapter Iv.— Introduction To Drafting. § 13

The Paper and the Scale.

§ 14. Linear Drawing Applied to Drafting.

Drafting, 93.

Choice of paper, 94.

To draw to scale, 95.

To cut the paper, 96.

To stretch the paper, 97.

To pencil a drawing, 98.

To ink a drawing, 99.

To make a tracing, 100.

Margins, border line, 101.

Conventions, 102.

§ 15. Lettering Applied to Drafting.

Choice of styles, 103.

Size and position of letters and figures, 104.

To make the letters and figures, 105.

The title of a drawing, 106.

Lettering on tracing-cloth, 107.

Chapter I

Instruments and Materials. § 1. Equipment.

1. Instruments and Materials Requn

ing and Lettering :

1 HHHHHH pencil.

1 HHHH pencil.

1 emery pad for sharpening pencils.

1 pencil-eraser, rubber.

1 ink-eraser, rubber.

1 doz. thumb-tacks or drawing-pins.

1 drawing-board, not less than 17"x24".

1 T square of same length as the board.

1 bottle water-proof drawing-ink, black.

1 sheet Whatman’s N. paper, Double Elephant si:

for the work in this course in Linear Draw-

1 45° triangle, 10", wrood, rubber, or celluloid. 1 60° triangle, 10", wood, rubber, or celluloid. 1 triangular boxwood scale, Architect’s.

1 piece chamois for cleaning pen.

1 irregular, or French, curve, K. & E. 19, T.

A. & Sons 16, or similar, celluloid.

1 penholder, swell body.

6 Gillott’s pens 303.

6 Gillott’s pens 404.

6 Leonardos 506 F, ball-pointed pens.

LINEAR DRAWING AND LETTERING.

1 case of instruments (every instrument numbered below bears the maker’s trade-mark as stated in the foot-note), as follows :

1 metal case of HHHHHH leads.

1 screw-driver and key-wrench (for adjusting instruments).

The instruments named above and the pocket-case named below are necessary for the course in Linear Drawing. The instruments named below are desirable for the Linear Drawing course and necessary for the work in advanced engineering courses. 1 5" hair-spring divider, T. A. 1423, Kern 642, K. & E. 608.

1 leather folding pocket-case, made to hold the following instruments :

2 5|" ruling-pens, 1 5-g" hair-spring compass (fixed needle-leg,

1 3|" bow divider, 1 3|" bow pen, 1 3|" pen, pencil, lengthening bar),

bow pencil, 1 screw-driver and key-wrench,

1 5" hair-spring divider, 1 metal case of HHHHHH leads.

* T. A. stands for T. Alteneder & Sons, 945 Ridge avenue, Philadelphia. Every instrument stamped “T. A.,” or “T. A. & Sons,” or “T. Alteneder & Sons.”

f Kern stands for Kern & Co., Aarau, Swiss. Every first-class instrument stamped “ Kern & Co.”

1 K. & E. stands for Keuffel & Esser Co., 127 Fulton street, New York. Every first-class instrument stamped “ K. & E. Co., N. Y., Paragon,” or “Keuffel & Esser Co.”

INSTRUMENTS AND MATERIALS.

It is well to purchase at the start, if possible, all the instruments named above as necessary or desirable, together with the case, which is made to hold all these and an additional pen. If the student cannot afford to do this, he buys the necessary instruments for the Linear Drawing course, and the case, and fills the vacant spaces in his case as additional instruments become necessary from time to time in his engineering courses. Two spaces in the case are made for pens, for a second pen will be needed before the first one is discarded.

For prices, see the catalogues of the firms named above.

§ 2. Care and Use of Instruments and Materials *

2. Drawing-Board. — Drawing-boards are made in different sizes, corresponding to regular sizes of drawing-papers. The simplest board is made of soft wood in one piece. This is improved by lining each sawed end with a narrow strip of hard wood to prevent the warping of the board, and to give a smoother surface for the head of the T square to slide on. The best boards are made up of narrow strips of soft wood held together by cleats so attached to the back of the board that shrinkage can be taken up at any time ; and each end is lined with a hardwood strip. It is necessary that the left end of the board be a straight-edge, and desirable that the near edge of the board be straight, and perpendicular to the left edge.

* For a fuller knowledge of the varieties of instruments and materials, the reader is referred to the catalogue of a mathematical instrument maker.

LINEAR DRAWING AND LETTERING.

3. Care of Drawing-Board. — The edges of the board should be kept free from indentation, and the upper surface smooth except for the holes made by thumb-tacks. The board, when not in use, should lie on a flat surface or stand nearly vertical on one end to prevent warping.

4. Use of Drawing-Board. — A rectangular piece of drawing-paper, cut to required size, is placed on the board so that the edges of the paper are parallel to those of the board (as determined by the T square if the paper is small compared with the board), and each corner of the sheet is tacked down with a thumb-tack. It may he necessary to use additional thumb-tacks on the paper edges to make it lie smooth.

5. T Square. — See Fig. 1. The simple T square has its blade rigidly fastened to its head. Others have an adjustable connection which permits setting the blade at any angle with the head. The cheaper T squares are made of wood, the head of one piece and the blade of another. The better grades have the inner edge of the head (which slides in contact with the board) and both edges of the blade, lined with narrow strips of hard wood or celluloid. The best are made of metal throughout.

6. Care of T Square. — The T square ought to lie flat on the drawing-board or be

hung, head down, against the wall, when not in use. Keep the edges of the blade free from

nicks. Do not use the T square as a hammer, nor the T blade as a guide for a knife.

The blade of the T square is said to be less apt to soil the paper if it is covered on its

lower side, to within a quarter-inch of each edge, with thin blotting-paper.

7. Use of T Square. — The upper or far edge of the T blade may be used as a guide for pen or pencil when drawing a straight line in any direction, but serves especially as a guide when drawing horizontal lines, i. e., lines perpendicular to the left edge of the drawing-board,

INSTRUMENTS AND MATERIALS.

and as a guide for one edge of the triangle while another edge is serving as a guide for the pen or pencil. Press the T head firmly against the left edge of the board before beginning to draw, and be sure that it remains there while drawing each horizontal or vertical line.

The inner edge of the T head and left edge of drawing-board being straight, all positions of the T blade are parallel when the T head is pressed firmly against, and moved along, the left edge of the board.

The T blade cannot be depended on to lie flat on the drawing throughout its length nor to keep its place without pressure from the hand. While drawing a line from the head to midpoint of blade, bear the left hand on the quarter-point nearest the head ; and when drawing a line along the outer half of the blade, press the blade down, with the left hand, at the quarter-point nearest the end of the blade.

8. Triangle. — Triangles are of many forms. Fig. 21 shows one form of triangle whose angles are 90°, 60°, and 30° (called a 30-60 triangle), and another whose angles are 90°, 45°, and 45° (called a 45° triangle). These are the forms most commonly used. Triangles are made in many sizes, and for those which have one 90° angle the size is given as the length of the longer perpendicular edge. Written in the order of cost, triangles are made of the following materials : wood, wood with lined edges, hard rubber, celluloid, German silver, aluminum, and steel.

9. Care of Triangle. — The triangles should be kept well cleaned to prevent their soiling the drawing-paper. To save the paper, the triangles should be moved over it as lightly as possible. If thin blotting-paper be pasted on the triangle to within a quarter-inch of the inner and outer edges it will be less apt to slip and soil the paper. This may not be desirable for the celluloid triangles, as it may detract from their value due to transparency. Triangles

LINEAR DRAWING AND LETTERING.

should, when idle for any length of time, lie on a flat surface to prevent warping. Do not use a triangle as a guide for a knife when cutting paper or trimming plates.

10. Use of Triangle. — Any edge of a triangle will serve as a guide (a straight-edge) to pen or pencil when drawing a straight line. The special use of a triangle is in drawing sets of parallel lines (Fig. 21). The altitude serves as a guide for vertical lines when the base is in contact with the upper edge of the T blade and the T head is pressed firmly against the left edge of the board. Sets of lines, making 45°, 30°, and 60° angles with the horizontal, can be drawn by using the triangles in connection with the T square, the head of which is pressed firmly against the left edge of the board.

11. Irregular, or French, Curve. — French curves are made of wood, hard rubber, and of celluloid. One form is shown in Fig. 19, which is one- third of the actual size.

12. Care of French Curve. — While idle, the curve should lie on a flat surface. Keep the edges of the curve free from indentations. Clean the curve often enough to prevent accumulations of oil and dirt, which rub off on the paper. Pasting strips of thin blotting-paper on the under side of the hard rubber will prevent its soiling the paper; but this device lessens the value of the celluloid as a transparent curve.

13. Use of French Curve. — This is explained in 64.

14. Drawing-Paper. — Drawing-papers are divided into three classes: I. “Drawing-paper,” II. Detail-paper, and III. Tracing-paper and tracing-cloth.

I. The term drawing-paper is usually reserved for the better grades of paper which are intended for drawings that are to be finished directly in pencil or ink. It is sold in sheets of different sizes, and in continuous sheets, or rolls, of different widths. It may be mounted ( i . e., backed by muslin) or unmounted. It is made in great variety of weight, surface, and quality, to

INSTRUMENTS AND MATERIALS.

suit all kinds of work. The surface may be “ H. P.” (hot-pressed, which is smooth), “N.” (not hot-pressed, which has a fine-grained surface), “ R.” (which is rough-grained), or “ egg-shell ” (which has a surface resembling a rough-surfaced egg-shell).

II. Detail-paper is the name given to the cheaper papers, suitable for rough and mediumfine pencil drawings which are to be finished by tracing, if at all. This, like the above, can be obtained in sheets and rolls, and of many weights and surfaces.

III. Tracing-paper is transparent, and sometimes used for tracing, in pencil or in ink, a design first drawn on a piece of detail-paper. Tracing-cloth is a transparent cloth (called also vellum), and is the material generally used for tracings, because of its toughness. It may be obtained in sheets of different sizes and in rolls of different widths. There are several grades.

15. Care of Drawing-Paper.— Sheets should lie flat when put away, or be rolled loosely. The rolls should be kept free from pressure, which breaks the surface. The paper should at all times be kept from dust and moisture. Spread and tacked on the drawing-board, the paper should be protected from dust, and the instruments and hands should come in contact with the paper as little and as lightly as possible. There is always more or less perspiration on the hands, and the T square and triangles are seldom so clean that the paper may not be soiled by their rubbing.

When making several drawings on one sheet, it is well to cover it with a protecting paper from which a piece is cut to expose that drawing which is being made at the time. If intervals of hours or days are to elapse between periods of work, the paper should be protected, as above, or removed from the board and put away.

The hard erasing which is required to remove the dirt from a soiled drawing injures the surface of the paper and the ink-lines which have been drawn. A neat drawing is produced by

LINEAR DRAWING AND LETTERING.

keeping the paper so clean that there is no need of rubbing and scrubbing at the end. If convenient, the hands should be washed frequently during a drawing period, especially in warm weather.

16. Use of Drawing-Paper. — The upper side of the paper is generally that which

shows the water-mark or trade-mark right side up. The rough side of egg-shell paper is for drawing. Many of the smoother and thinner papers are about the same on both sides. Tracing-cloth may be used either side up. Some draftsmen condemn the use of the rough side because ink-lines made on this side are ragged, and erasures cannot well be made. Others use the rough side, because drawings so made lie flat instead of rolling up, and pencil work can be done on

this side. If the smooth side is to be used for ink-lines, it should first be dulled by rubbing

with pumice powder. The powder must be thoroughly removed before inking the lines, for it clogs the pen.

When about to touch ruling- or common pen to paper at' any place, press the paper flat against the board and keep it there till the line is done and the pen has been lifted from the

paper. Otherwise there will usually be made a blot or a tail at each end of the line.

17. Pencil.— Faber’s HHHHHH or Koh-i-noor HHHHHH pencil should be used for all drawing in this course, except that for coarse work and lettering the HHHH grade should be used. No accurate drawing can be done without smooth lead of proper hardness.

18. Care of Pencil. — For the cone-point (see Fig. 14) cut away the wood at the end opposite the printing, to expose at least one-half inch of lead. Rub the exposed lead flatwise over fine-grained emery-paper while twirling the pencil between the thumb and fingers, till the sharptipped cone-point is formed. Next, rub the lead in a similar manner on rough-surfaced paper until the tip of the cone-point, when viewed endwise, is invisible. This point is easily broken, and it must rest on the paper with very little pressure while drawing a line. The cone-

INSTRUMENTS AND MATERIALS.

point is used where the greatest accuracy is required, as in Graphics, but is not as serviceable as the chisel-point for drawing lines which must be distinct enough to show through tracing-cloth. The dull cone-point is used for printing figures and descriptions on a drawing, and for free-hand curves.

For the chisel-point (Fig. 13), expose a half-inch of lead. Rub two opposite sides of the lead flatwise on the emery-paper, till a sharp chisel is formed. Next, repeat the rubbing on drawing-paper until the edge of the chisel is invisible. The chisel-point, when applied with pressure, rules a line which is fine enough for working-drawings, and yet distinct enough to show clearly through tracing-cloth. The cone-point, of equal sharpness and applied with the same pressure, either breaks, or wears away too rapidly. The cone-point admits of greater precision, and, for drawings which are to be redrawn directly in ink, rules sufficiently distinct lines.

After drawing each long line, or a few short ones, examine the pencil-point, and if it reflects light when viewed endwise, resharpen by rubbing on a piece of drawing-paper. The emery-paper need be used only when resharpening on paper takes too much time. It is well to have in use two pencils, one with cone- and the other with chisel-point. Neither chew the pencil nor wet the lead in the mouth.

19. Use of Pencil. — A hair-line is drawn with the sharp cone-point, with slight pressure. It is distinctly visible by diffused light, but may be invisible when the paper reflects light to the eye from a window. It is easily erased, leaving no trace. The intersection of two hair-lines determines a point with precision. (A determined point should be marked faintly with needle-point or pencil tip, and enclosed, for ready finding, in a small circle drawn free-hand with pencil.)

The most accurate drawings are first constructed with hair-lines. Afterward, some of the

LINEAR DRAWING AND LETTERING.

lines may be made heavier ; but when retracing a hair-line with the pencil, make a break in the heavy line at each accurately determined point, that it may not be obliterated.

In accurate work, hold the pencil as carefully as the ruling-pen. Hold the pencil perpendicular to the paper, with the exception of a slight slant in the direction of motion. When drawing any line, free-hand or otherwise, with the pencil, do not bear down enough to make a groove in the paper, unless absolutely certain that no part of the line will require erasure.

The chisel-pointed pencil should be so held that the chisel edge has the direction of the line which it is ruling.

If the guide is pressed firmly on the paper at every point as it is reached, the pencil may be given an outward slant to bring the tip of the lead against the lower edge of the guide. But if the pencil is thus held, and the guide is in contact with the paper only for portions of its length, the pencil point will trace a crooked line.

Slant the pencil neither outward nor inward, reaching for a point through which the line is to be drawn ; but bring the guide to such a position that the pencil tip will precisely touch the point when the pencil is held in correct position, against the guide.

20. Ruling-Pen. — (Fig- 20.) Ruling-pens are made in three or more sizes. The simplest have fixed blades. The outer blade, in one form, is so made that its upper end acts as a spring to throw the blades a little apart when released by the set-screw. The blades of the hinge-blade pen may, on releasing the set-screw, be thrown open through an angle of 90° or more. Other pens are so made that the blades can be opened wide and again closed, without disturbing the set-screw. Some pen handles are made to unscrew, and carry a needle-point, which may be used for marking points with precision, and for transferring a drawing from one sheet to another, by pricking through the original. Pens are also made for special work, as the curve-pen for drawing contours, the railroad-pen, and the border-pen.

INSTRUMENTS AND MATERIALS.

21. Care of Ruling-Pen. — (Fig. 20.) The nibs of the ruling-pen should be of the same width, so that, when brought together, one nowhere overlaps the other. They should be so sharp that, when viewed endwise, they reflect no light, and yet not sharp enough to cut the paper. It is easy to break a piece from a sharp nib by careless handling. A roughness of the points may be invisible to the naked eye and yet make the pen scratch the paper (Fig. 25). When the pen scratches, or is dull (as shown by reflected light at the points), it should be sharpened by rubbing the outside surfaces of the nibs on a fine Arkansas oilstone, while holding the pen at an angle of about 20° with the stone. To make the points of equal length, draw the pen lightly across the stone, as in drawing a line on paper ; at the same time rock the pen, in the plane of motion, to round the nibs. Frequently examine the points through a magnifyingglass during the grinding. The frequency of required sharpening depends on the hardness of the steel in the points, and on the use given the pen. Detail-paper wears a pen rapidly, and it is not economy to use such paper for drawings which are to be inked. In some offices a pen which is in constant use is sharpened daily. Usually a beginner should practice grinding an old pen before trying to sharpen a new one. An instrument-maker will properly sharpen a pen for about twenty-five cents.

Do not let the ink ary in the pen. Before laying it aside for a few minutes, shake out the ink and wipe the nibs, inside and outside, with cloth or chamois. At the end of a period of work, wipe or wash off all traces of ink, and put the pen away with its nibs bright and thoroughly dry. Fig. 25 is an enlarged sketch of the inner face of the nib of a ruling-pen which has not been kept scrupulously clean.

22. Use of Ruling-Pen . — The opening between the nibs of the pen is made, by means of the set-screw (Fig. 20), equal to the width, or thickness, of line to be drawn. When setting

LINEAR DRAWING AND LETTERING.

the pen for fine lines be careful that the nibs are not made to touch each other. Usually the required opening between the nibs is determined by trial after the pen is filled with ink. Once set to give the desired width of line, the set-screw should not be touched until it is required to draw lines of another width, or to clean the pen. A piece of paper, cloth, or chamois is run between the nibs without disturbing the setting, to remove ink which, thickened by evaporation, partially closes the outlet.

To fill the pen with inlc: Take the pen to the bottle. Hold the pen, nibs up, between the thumb and first finger, and the bottle (which rests on the table) between the little finger and palm, of the left hand. Remove the stopper from the bottle with the right hand, and, by means of the quill inserted in the lower side of the stopper for the purpose, transfer the ink, drop by drop, from bottle to pen. Move the quill point upward between the nibs, if necessary, to insure the complete transfer of the ink drop. The pen is too full only when the ink spills out on a slight, sudden motion of the pen. A little experience will determine the proper amount of ink to put in the pen. Do not wait till the pen is empty to refill it, for the width of the line ruled changes slightly with the supply of ink. Always keep the exterior of the nibs absolutely free from ink ; otherwise ink will come into contact with, and run under, the guide, making a blot. Furthermore, ink, wet or dry, on the exterior of the nibs, interferes with the ruling of clean-cut lines.

To rule a line : Hold the pen perpendicular to the paper, with the axis of the set-screw perpendicular to the direction of the line to be drawn, and with the screw head on the far side of the pen. Move the pen from left to right. The weight of the hand is carried by the third and fourth fingers, which rest upon, and move along, the guide. Ho not press the pen against the guide, for this tends to close the pen opening. In beginning to draw a line, after the pen has been placed at the starting-point, put the head directly in front of the pen, to see that the

INSTRUMENTS AND MATERIALS.

handle has no slope to right or left. Then, place the head in such a position that the eyes are about ten inches above the guiding edge, and about ten inches to the left of the pen. With the head in this position, the inside faces of the blades are equally visible when the set-screw axis is perpendicular to the direction of the line to be drawn. In moving the pen to the right to rule the line, the hand should swing neither about the elbow nor shoulder, as a pivot. Simply move the body to the right, carrying the hand and arm with it. Beginners usually make the mistake of placing the head directly above the pen nibs, to see which then requires the pen handle to be thrown to the right. See Figs. 40, 41.

Reach neither in nor out, with the pen, to make the nibs pass through a given point ; but bring the guide to such a position that the nibs will pass precisely through the point while the pen is held correctly, in contact with the guide. Study Figs. 6, 7, 8, 9, 10, and 11 in connection with this article.

23. Ink. — Formerly all drawing-ink was prepared for use, day by day, by rubbing stick India-ink on the bottom of a dish wet with a small quantity of water. Now, ready-made liquid drawing-inks are most commonly used. These are made water-proof and non-water-proof, in black and in colors. Water-proof ink should be used for most drawings. Non-water-proof may flow a little more freely than the water-proof ink, but a drawing made with the former is easily smeared by handling. Do not waste time and make poor lines in attempting to economize by using the dregs of an old bottle.

24. Care and Use of Ink. — Keep the bottle well corked at all times when not actually taking out ink, which rapidly deteriorates by evaporation. Keep the bottle off the drawing. The ink may be thinned by adding some drops of water, alcohol, or ammonia, when it has become too thick, but this mixture is not as good as new ink. Remove ink at once from all

LINEAR DRAWING AND LETTERING.

surfaces to which it has come by accident. Leave ink to dry neither on the ruling- nor lettering-pen, as it corrodes, and thus injures, the nibs. Flies take up ink, and should be kept from drawings, especially those made on tracing cloth, while ink-lines are wet.

To supply the ruling-pen with ink, follow directions under 22. The lettering-pen is dipped in the ink as in ordinary writing, but the stopper must be replaced in the bottle after each dip.

25. Rubber Pencil-Eraser. — The best eraser is that which wears away so rapidly as always to present a fresh surface. Erasers harden with age, and finally injure the paper without properly removing pencil lines. Before applying it to a drawing, the end of the eraser is cleaned by rubbing it on a piece of fresh paper. Erase gently, especially over ink lines. Too energetic erasing dulls ink lines and roughens the paper surface. The rubbing should be done in the direction of ink lines rather than across them. If, in spite of care, a drawing becomes grimy, clean it with stale bread (26).