In some respects the surface enrichment of clay is similar to that of wood as, for example, the similarity produced by inlays in clay and in wood. On the other hand the enrichment of clay is unhampered by the restricting effects of unequal resistance of the material, such as the grain of wood. Again it is limited to those effects or forms of enrichment that are capable of withstanding the intense heat to which ceramic decoration is subjected. See Frontispiece.

Before proceeding with a design it is well for one to understand clearly the possibilities of clay enrichment. He must know what kind of designs are best suited to clay as a medium, to the intended service, and to the ultimate application of the heat of the pottery kiln. Without entering into technicalities let us briefly discuss the following processes. The first three deal with finger and tool manipulation of the clay body and are consequently the simpler of the processes. The last five are concerned chiefly with the addition of coloring pigments either to the clay or to the glaze and are, therefore, more complex in character.

Processes

Rule 9a. Surface enrichment of clay must be so designed as to be able to withstand the action of heat to which all ware must be submitted.

Rule 9b. Incised, pierced, and modeled decoration in clay should be simple and bold and thus adapted to the character of the material.

1. This is the simplest form of enrichment, a process familiar to the earliest primitive potters and appropriate now for beginners. It consists of the process of lowering lines or planes into the clay body to the depth of from one-sixteenth to one-eighth of an inch. These lines or planes should be bold and broad. They may be made with a blunt pencil or a flat pointed stick. A square, rectangular, or round stick may be used as a stamp with which to form a pattern for incising. Illustrations of simple incising may be found in Figures 283, 284, 295, 319, 330. The tiles shown are about six inches square.

2. This process is less common and, as its name implies, is carried out by cutting through the clay. It may be done with a fine wire. Either the background or the design itself may be thus removed. The effect produced is that of lightening an object such as the top of a hanging flower holder, a window flower box, or a lantern shade.

3. By adding clay to the main body, and by working this clay into low relief flower or geometric forms, one has the basic process of modeling. The slightly raised areas of clay form a pleasing play of light and shade that varies the otherwise plain surface of the ware. The process should be used with caution, for over-modeling, Figure 325, will obstruct the structural outlines and, because of its over prominence as decoration, will cease to be surface enrichment. In the technical language of the designer over-modeling is an enrichment which is not subordinated to the surface. In articles intended for service this high relief modeling is unsanitary and unsatisfactory.

Figures 286 and 287 show incising with slight modeling, while 324, 328, and 329 are examples of more complex enrichment.

With the introduction of the second group comes an added interest and difficulty, that of the introduction of color. Pigments that will withstand the application of heat are suggested at different points.

4. This process consists of removing certain areas from the clay body to the depth of one-eighth inch and filling in the depression with tinted clay. Tints formed by the addition of ten per cent or less of burnt umber or yellow ochre to the modeling clay will give interesting effects. Figures 284, 285, 320, and 321 show forms which may be developed by this process.

Sgraffito, an Italian process, is more difficult than inlaying, but the effect is similar. A thin layer of colored clay is placed over the natural clay body, and the design is developed by cutting away this colored coating in places, thus exposing the natural clay body. Figure 306. There are variations of this plan that may be attempted by the advanced designer.

5. Slip is clay mixed with water to the consistency of cream. For slip painting this mixture is thoroughly mixed with not more than ten per cent of coloring pigment as represented by the underglaze colors of the ceramist. This thick, creamy, colored slip is then painted on the surface of the clay body while damp, much as the artist would apply oil colors. The ware, when thoroughly dried, is glazed and fired, which produces the effect shown in Figures 290, 291, and 327. The color range is large; almost any color may be used with the exception of reds and strong yellows. A colorless transparent glaze should be used over beginner's slip painting.

6. This process refers to the direct introduction of the colored pigment into the glaze. By varying the glaze formula we may have a clear, transparent, or glossy glaze similar to Figure 317, a dull surfaced opaque effect, termed a matt glaze, Figure 332; or a glossy but opaque faience glaze similar to the blue and white Dutch tiles. There are other forms such as the crystalline and "reduced" glazes, but these as a rule are far beyond the ability of the beginning craftsman in ceramics.

It is possible to use these three types of glazed surface in various ways. For example, a vase form with an interesting contour may be left without further surface enrichment except that supplied by clear glaze or by a colored matt similar to certain types of Teco Ware. It is likewise possible to apply transparent glazes over incised designs, inlay or slip painting, increasing their beauty and the serviceability of the ware. A semi-transparent glaze is sometimes placed over slip painting giving the charm inherent to the Vellum Ware of the Rookwood Potteries. Figure 332. Greens, blues, yellows, and browns, with their admixtures, are the safest combinations for the craftsman who desires to mix his own glazes.

7. This process may be seen in the examples of Newcomb Pottery illustrated particularly in Figure 314 or 326. The underglaze pigment is thinly painted upon the fired "biscuit," or unglazed ware. A thin, transparent glaze is then placed over the color, and in the final firing the underneath color shows through this transparent coating, thus illustrating the origin of the name underglaze or under-the-glaze painting. Sage-green and cobalt-blue underglaze colors are frequently used in Newcomb designs with harmonious results. The outline of the design is often incised and the underglaze color, settling into these channels, helps to accentuate the design. Figure 314.

8. This is popularly known as china painting and consists of painting directly upon the glazed surface of the ware and placing it in a china kiln where a temperature between 600 degrees and 900 degrees C. is developed. At this point the coloring pigment melts or is fused into the porcelain glaze, thus insuring its reasonable permanence. Figure 302.

The eight processes briefly described may be readily identified on the plates by referring to the figures corresponding to those which number the processes and are added to each figure number. Two processes are sometimes suggested as possible for one problem.

Different clay forms require different modes of treatment. To simplify these treatments will now be our problem. It has been found convenient to form four divisions based upon the general geometric shape of the ware. The first, Plate 47, includes rectangular and square areas; the second, Plate 48, shallow and circular forms; the third, Plate 49, low cylindrical forms; and the fourth, Plate 50, high cylindrical forms. The first three divisions have distinct modes of design treatment, while the fourth interlocks to a considerable extent with the third method. We shall now consider each plate with reference to its use and possible forms of enrichment. For the sake of brevity, the results have been condensed into tabulated forms.

Each geometric form or type on these plates has not only distinctive methods of design treatment but characteristic locations for placing the design as well. These places or zones of enrichment have been indicated in the following tabulated forms by the letters in parentheses. There are a number of zones for each plate. For example, Plate 47 has its distinctive problems as tiles, weights, etc., and five characteristic zones of enrichment described on pages 153-155 and indicated by the letters A, B, C, D, E, followed by a brief description of that zone. Each zone is still further analyzed into its accompanying type of design, inceptive axis, point of concentration, and illustrations. Each plate has the proper zone of enrichment immediately following the figure number and in turn followed by the process number.

Problems: Tiles for tea and coffee pots, paper weights, window boxes; architectural tiles for floors, and fire places.

(A) Zone of Enrichment: In the margin.
Reason for Choice: Central area to be devoted to zone of service requiring simplicity in design.
Type of Design: Bands or borders.
Inceptive Axis: For corners; the bisector of the angle.
Points of Concentration: The corners and, if desired, at equal intervals between the corners.
Illustrations: Figures 283, 284, 286, 287, 288.

(B) Zone of Enrichment: center of surface, free ornament.
Type of Design: Initials, monograms, street numbers, geometric patterns, and other examples for free ornament. A star or diamond is not appropriate enrichment for a square area unless properly related to the contour by connecting areas.
Inceptive Axes: Vertical or horizontal diameters or diagonals.
Points of Concentration: Center of embellishment.
Illustrations: Figure 285.

(C) Zone of Enrichment: full surface enrichment in a horizontal position.
Type of Design: A symmetrical pattern generally radiating from the geometric center of the surface and covering at least two-thirds of the surface.
Inceptive Axes: Diameters or diagonals of the area.
Points of Concentration: At the corners or the center of the outer margin; at geometric center, as in a rosette.
Illustrations: Figures 283, 289, and 291.

(D) Zone of Enrichment: full surface enrichment in a vertical position.
Type of Design: A symmetrical pattern with a strong upward movement and covering more than one-half of the surface.
Inceptive Axis: The vertical center line.
Point of Concentration: Upper section of the surface.
Illustrations: Figures 290 and 292.

(E) Zone of Enrichment: free balance over full surface.
Type of Design: Semi-decorative motive preferably covering the entire surface.
Inceptive Axis: Masses freely balanced over the geometric center of the area.
Point of Concentration: Near, but not in the exact center.
Illustrations: Figures 293, 294, 295, 296, 297, 298.
Note: The points of concentration should be accented by slight contrast of value and hue. See chapters on color.

Problems: Plates, saucers, ash trays, card receivers, almond and candy bowls.

(A) Zone of Enrichment: margin of interior surface; margin of exterior surface.
Type of Design: Bands or borders thoroughly related to the structural contours. Bands for exterior enrichment may be placed directly on the contour, Figures 299 and 301, thus forming an accented contour (F) or slightly removed from it, as in Figure 300.
Inceptive Axes: For interior surfaces, the radii of the contour circle generally supply the axes of symmetry.
Points of Concentration: For interior surfaces, the points of concentration may be placed in or near the radii of the area.
Illustrations: Figures 302, 303, 304, 305, 306.

Problems: Cups, pitchers, steins, nut and rose bowls, low vase forms.

(A) Zone of Enrichment: upper margin of exterior.
Type of Design: Borders of units joining each other or connected
by bands or spots acting as connecting links. Rule 9c.
Inceptive Axes: Vertical elements of the exterior surface. Elements are imaginary lines dividing the exterior surface into any given number of vertical sections. Elements used as center lines form the axes of symmetry about which the butterfly of Figure 308 and similar designs are constructed.
Points of Concentration: On each vertical element.
Illustrations: Figures 308, 309, 310, 311, 312, 316.

(D) Zone of Enrichment: full vertical surface.
Type of Design: Extended borders with strongly developed vertical lines or forms. Less than one-half of the surface may be covered.
Inceptive Axes: Vertical elements.
Points of Concentration: In upper portion of vertical elements, hence in upper portion of area.
> Illustrations: Figures 307, 314, 317, 318.

(E) Zone of Enrichment: free balance of full surface. (See D, above).
Illustration: Figure 315.

Problems: Vases, jars, pitchers, tall flower holders, covered jars for tea, crackers, or tobacco.

(A) Zone of Enrichment: margin of exterior.
Type of Design: Borders of geometric units, freely balanced floral units, and other natural motives placed in upper margin of mass.
Inceptive Axes: Vertical elements of cylinder.
Points of Concentration: In upper portion of vertical elements.
Illustrations: Figures 319, 320, 321, 327, 331, 332.

(D) Zone of Enrichment: full surface of exterior.
Type of Design: Free of formal conventionalized unit repeated on each vertical element. The units may be juxtaposed or may be connected by bands or similar links.
Inceptive Axes: Vertical elements of cylinder.
Point of concentration: In upper portion of vertical elements.
Illustrations: Figures 322, 323, 324, 326, 328, 329.

The reader should carefully consider the postulate and various divisions of Rule 7 and try to apply them to the material now under consideration. Acknowledgment is made for material supplied by the Rookwood Potteries for Figures 288, 289, 292, 293, 294, 297, 298, 315; 327 and 332; Newcomb Potteries, Figures 314, 316, 317, 318, 326; Teco Potteries, 329; Keramic Studio Publishing Company, 302, 307, 308, 310, 312.

INSTRUCTION SHEET

Plate 51 illustrates the marginal surface enrichment of low cylindrical forms, with part surface enrichment of two higher forms.

SUMMARY OF DESIGN STEPS

(a) Draw primary mass:

For square or rectangular areas draw square rectangle, etc.

For shallow circular forms draw a circle.

For low cylindrical forms draw a rectangle; subdivide this if desired by a unit of measurement into two horizontal divisions.

For high cylindrical forms draw a rectangle; subdivide this if desired by a unit of measurement into two or three horizontal divisions. Rule 5e.

(b) Design simple contour enrichment based upon these units of measurement.

(c) Locate zone of enrichment.

(d) Draw inceptive axes:

For square or rectangular areas draw diameters, diagonals, or both.

For shallow circular forms draw radii of the primary circle; concentric circles for bands.

For low cylindrical forms draw the elements of the underlying cylindrical form for extended borders or lines paralleling the top or bottom of the primary mass for bands.

For high cylindrical forms draw inceptive axes similar to low cylindrical forms.

(e) Locate points of concentration in these inceptive axes.

(f) Determine manner and amount of surface enrichment.

(g) Add leading lines and develop these into surface enrichment.

(h) Make potter's working drawing, full size (See Plate 26). Add the necessary amount for shrinkage and otherwise prepare the drawing for potter's use.

(i) Make a paper tracing of the surface enrichment for transfer to clay body and cut a zinc or tin template as a contour guide in building the form.

SUGGESTED PROBLEMS

Design a cider or chocolate set with appropriate surface enrichment.

Design an architectural tile 6 in. by 9 in. for accenting a brick fireplace in the home.

SUMMARY OF RULES

Rule 9a. Surface enrichment of clay must be so designed as to be able to withstand the action of heat to which all ware must be submitted.

Rule 9b. Incised, pierced, and modeled decoration in clay should be simple and bold and thus adapted to the character of the material.

Rule 9c. A border should not be located at the point of greatest curvature in the contour of a cylindrical form. The contour curve is of sufficient interest in itself at that point.

REVIEW QUESTIONS

1. Compare the surface enrichment of clay with that of wood.

2. State a major requirement of a good pottery design.

3. Give the broad divisions into which it is possible to divide the decorative processes of clay surface enrichment.

4. Name and briefly describe eight methods of enriching the surface of clay.

5. What precautions should be exercised with regard to the use of incised, pierced, and modeled decoration?

6. Should a border be placed at the point of greatest curvature of the contour? Give reasons.

7. Name method of classifying structural forms in clay into four groups.

8. State problems and possible zones of enrichment in each group. Give reasons for choice.

9. State type of design unit, conventionalized, natural or artificial forms, location of inceptive axis, points of concentration, and process for each zone of enrichment.

10. What is an element of a cylindrical surface?