Industrial Arts Design Part 20

FIGURE 281.--Filling the Saggars before Firing]

[Sidenote: Decorative Processes of Surface Enrichment]

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.

[Ill.u.s.tration: _Courtesy of The Rookwood Potteries_

FIGURE 282.--Stacking the Kiln]

[Sidenote: Forms of Manipulation]

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._

[Sidenote: Incising]

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. Ill.u.s.trations of simple incising may be found in Figures 283, 284, 295, 319, 330. The tiles shown are about six inches square.

[Sidenote: Piercing]

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.

[Sidenote: Modeling]

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.

[Ill.u.s.tration: SURFACE ENRICHMENT OF CLAY

RECTANGULAR AND SQUARE AREAS

PLATE 47]

[Sidenote: Introduction of Coloring Pigments]

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.

[Sidenote: Inlay]

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.

[Sidenote: Slip Painting]

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.

[Sidenote: Colored Glazes]

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.

[Sidenote: Combinations]

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.

[Ill.u.s.tration: SURFACE ENRICHMENT OF CLAY

SHALLOW CIRCULAR FORMS: PLATES, ETC

PLATE 48]

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.

[Sidenote: Underglaze Painting]

7. This process may be seen in the examples of Newcomb Pottery ill.u.s.trated 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 ill.u.s.trating 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.

[Sidenote: Porcelain or Overglaze Painting]

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.

[Sidenote: Cla.s.sification of Structural Clay Forms]

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.

[Ill.u.s.tration: SURFACE ENRICHMENT OF CLAY

LOW CYLINDRICAL FORMS

PLATE 49]

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 a.n.a.lyzed into its accompanying type of design, inceptive axis, point of concentration, and ill.u.s.trations. Each plate has the proper zone of enrichment immediately following the figure number and in turn followed by the process number.

[Sidenote: Square and Rectangular Areas, Plate 47]

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