Archive for May, 2006

Polychrome

In a polychrome decoration the design is painted directly on the piece with colored glazes. The main problem with this type of decoration is to prevent one color from flowing into another. For this reason you must use glazes that are hard enough to remain stationary and prevent distortion of the design. Plan a design of a simple, bold nature, with the colors far enough away from each other to allow for any running since even the hard glazes will move a little in the firing. An intricate design painted with glazes invariably winds up as a mere jumble of color. Carefully execute the areas of color on paper and test the chosen glazes before starting any decorating.

Polychrome decoration may be done in several ways. One method is to glaze the entire piece with a clear or light colored glaze first and then paint a design over the unfired glaze with deeper, contrasting glazes. Painting one glaze over another is a bit tricky. To prevent difficulty, spray or brush on a light coat of gum tragacanth over the background glaze before applying the design; this enables the brush to slide smoothly over the surface rather than dragging as it is apt to

Illustration 89
For a polychrome decoration, draw the design carefully on the piece.

Illustration 90
Then incise the lines of the design with a sgraffito tool.

do over an unfired glaze. It is also possible to reverse the procedure: paint the design first with colored glazes, then spray a clear or light colored transparent glaze over the entire piece.

Illustration 91
Apply colored glazes in the enclosed areas and scrape glaze from the incised lines.

Illustration 92
Dots of opaque glaze are here added as an accent.

Wax resist

Resist decoration has been covered in a preceding chapter (see pages 55-56). The procedure varies but slightly when applied to glazes. As with engobes, melted paraffin or liquid rubber may be used for the design. After the resist material has been applied, a colored glaze may be sprayed, dipped or brushed on the piece. The main difference to remember when using this technique with glazes is that the design area will be un-glazed in contrast to the glazed background. This is often very attractive, especially if the clay body is red or buff. If the body is white and you desire this particular effect, give the piece a coat of underglaze color, bisque fire it and then use the resist method. Use an opaque glaze that will cover the underglaze color in the non-resist areas.

If you want to have the design area glazed as well as the background, apply the background and then remove the resist material either by firing in the case of wax, or by peeling off the hardened liquid rubber. Then the entire piece may be sprayed with a light coat of clear glaze or a contrasting colored glaze may be brushed on the resist area. When you use a resist technique with glazes be sure to apply a hard glaze as soft glazes would run, distorting the resist design.

Glaze intaglio

A technique similar to wax resist, although more textural in effect, is glaze intaglio. This is a method by which cut areas are filled with glaze to contrast with the raised areas, which are left unglazed. Scratch the entire design on leather hard green ware, then gouge out the intaglio areas (the areas to be filled with glaze) to a depth of approximately %”. The carving may have to be deeper if you use a soft glaze, but Vs” is usually suitable for most glazes. The green ware should be fairly thick so that the carving does not penetrate the walls of the piece.

Spray the glaze on the piece, allow to dry and then remove the glaze on the raised areas by scraping it off with a clay modeling tool. Remove any glaze still remaining with a damp sponge. It is important that the raised areas be completely free of glaze, because the whole effect of intaglio depends upon the contrast between the smooth glazed areas and the rougher texture of the unglazed areas. If spraying is not advisable, brush the glaze into the cut areas and allow it to dry, then scrape the excess glaze off the raised portions.

As the term indicates, drip glazing is a method of decorating in which a very soft glaze is allowed to drip down over another glaze. This type of glazing should be used only on deep bowls or vases since the piece must have some depth if the glaze is to drip down.

The base or background glaze may be either a hard or soft glaze, depending upon the effect desired, but the drip glaze should be soft enough to move during the firing. When a hard glaze is used as the base glaze, the decorative effect will depend solely upon the soft drip glaze that is applied over it. However, if a soft glaze is used as a background, it too will move, pulling the drip glaze along with it and producing an altogether different effect.

After the entire piece is covered with the base glaze, apply the drip glaze to the edge of the piece. The heavier the application, the more dripping will result and the pattern of dripping will give a curtained effect. A lighter application will result in long, thin drips. The pattern will vary also according to the shape of the piece.

Very little control is possible with drip glazing and many of the effects are accidental and difficult to duplicate. The technique is such that a great deal of experimentation is required and, even then, the results are not always predictable, but as the entire field of ceramics is more or less unpredictable, this should not necessarily be considered a drawback. It is, in fact, one of the factors that makes ceramics the fascinating craft that it is.

One of the most fascinating ways of decorating ceramics is by means of glazes, for glazes can produce a jewel-like richness of color and a contrast of textures rarely achieved with other decorating methods. There is such a wide variety of glazes that the decorating possibilities are almost endless; here, indeed, is ample opportunity for the imagination to run riot and the curious mind to explore. Once you acquire a fundamental knowledge of the behavior of glazes (see Chapter IV), you need only apply your good taste and ingenuity to the stimulating task of producing ceramics of great beauty and individuality.

Glazing the inside of a vase

Regardless of the manner in which a vase or other container has been decorated on the outside, the attractiveness of the piece can be greatly enhanced by the application of a different color glaze to the inside. This should be done before the outside is decorated so that any excess glaze that may land on the outside surface can be removed safely.

Choose a brushing-on glaze that will provide the most interesting color contrast to the planned decoration. Fill the vase approximately one-third with the glaze. Cover the top with one hand to prevent the glaze from spilling and rotate the vase in such a way that the inside becomes covered with glaze. Then pour out whatever glaze is left over and turn the vase upside down on a newspaper to drain.

After the inside has been glazed the outside may be decorated immediately, but not glazed. The vase should be allowed to dry overnight before it is glazed on the outside. This will give the chemical water a chance to escape and thus prevent bubbles, cracks or other defects in the fired piece. (This applies only to green ware since bisque ware may be glazed on the inside and outside without a drying period.)

Illustration 85

Illustration 87

85. To glaze the inside of a vase, fill it one-third full with a glaze that contrasts with that planned for the outside.
86. Rotate the vase so glaze covers the inside.
87. Pour out the excess glaze. The last step is shown on page 78.

Illustration 88
Turn the vase upside down to drain, resting it on a jar lid at a slight angle.

Banding

Applying a band of color to a plate, bowl or vase involves essentially the same procedure as spinning a color. Banding, however, is done with a brush rather than with a sponge and the result is a definite band of color as contrasted with the blended spirals of color on a spun piece. As with spinning, a record player or decorating wheel is used. The piece is carefully centered and the wheel or player set in motion.

Your brush must be well saturated with color before it is placed on the revolving piece. Place the brush flat against the piece and hold it in that position while the band of color is being formed. Banding may be used as a trim or the entire piece may be decorated with bands of several colors. In the latter case, sgraffito designs applied over the banding will add a great deal of interest to the piece.

Sandpaper accents

The use of sandpaper strokes as a decorative accent gives much the same effect as dry brush, except that the color is taken off rather than put on. This technique shows to best advantage on a fairly solid background with the main design areas defined by sgraffito lines. It is also effective for scraping highlights on a more involved and colorful design.

The rough grade of sandpaper is best in both cases as it produces a more interesting texture. Tear off a small piece of sandpaper and simply scrape off the color where the accent is desired. Do not overwork the scraping; as with dry brush, the finished decoration should be crisp and spontaneous. Just a few, quick strokes with the sandpaper will give an appearance of depth to a simple decoration.