Archive for June, 2006

Crackle glazes

Crackle glazes, whether clear or opaque, are effective on almost any ceramic piece and, when stained, are among the most attractive ceramic finishes available to the decorator. You can apply a clear crackle glaze over an underglaze decoration as you would an ordinary clear glaze. The advantage of using a clear crackle over a decoration is that the design itself can be very simple. Background decoration may be eliminated, since the pattern of crazing provides sufficient background interest.

A white opaque crackle glaze makes a very nice background for a Majolica decoration, or an accent on a red clay piece, or you can use it as the sole means of decorating a piece. It is also a good glaze to keep in mind for an interesting variation in a polychrome decoration. You may also tint a clear crackle with underglaze colors or oxides for a more colorful effect.

To use a crackle glaze to its most decorative advantage you should stain the piece after it has been fired to emphasize the crazing pattern. Cover the crackle glazed surface with a diluted application of India ink or liquid shoe polish and then wipe it off with a rag. The stain will sink into the minute bisque cracks of the crackle glaze, forming a definite pattern of crazing. To achieve the color you desire do not attempt to apply the stain full strength since it is difficult, if not impossible, to remove it from the tiny cracks of crazing. It is better to make several diluted applications until you get the color you want.

A crackle glazed piece, it should be remembered, is not waterproof. You cannot use it to hold liquids unless you glaze one wall of the piece with a non-crackle glaze or unless the clay body itself is vitreous, as in the case of stoneware and porcelain. And you can’t use a crackle glaze piece that has been stained as a food container, since the stain may wear off in time.

Illustration 101
Crackle glazes are among the most attractive ceramic finishes available. The pattern of crazing provides the only decoration needed. Here a white opaque crackle glaze gives just the right finish to the figurine.

It is possible to produce a waterproof piece with a crackle effect, although not without risks. To do this, glaze the piece with a non-crackle glaze and underfire it (about two or three cones under the maturing temperature). When the kiln cools enough to permit removal of the ware (although the ware should be hot), take the piece out and plunge it into cold water. The temperature shock will cause the glaze to craze-but it may also cause the piece to break. If it survives, rub underglaze color over the piece so that it sinks into all the crazing cracks and then wipe off the excess. Fire the piece again, this time at the full maturing temperature. The cracks in the glaze will close, leaving the underglaze pattern of crazing. The piece is now waterproof, as there is no more actual crazing, but it retains a crackle glaze appearance.

Keywords: Ceramic Decorations, Ceramics Decor, Ceramics, Painting

Pooling a jewel glaze is merely a matter of applying a soft glaze in large amounts to the entire inside surface of a dish or similar container. When fired, the glaze will run down the sides and form a pool at the bottom of the dish. Upon cooling this becomes a thick layer of glass, jewel-like in color and depth.

Another way to pool a jewel glaze is to give the inside of the dish a coat of fairly hard glaze and then apply a generous amount of jewel glaze only to the bottom (not the underside) of the dish. This method insures proper coverage of the entire piece and also permits the use of a color contrast. For the most effective result, use colors that are related to one another; that is, if you use a light turquoise as the base glaze, use a dark blue or dark green jewel glaze for pooling. Do not, for example, apply a green jewel glaze over a brown glaze, because the full brilliance of the green will be muddied by the brown glaze underneath, destroying the jewel effect.

Naturally a pattern should not be at-temped because of the fluidity of the very soft glaze. It is, however, possible to achieve a very simple pool design. One interesting type of design is a star shape. First trace the outline of the star on the bottom of the dish,

Illustration 100
A jewel glaze is pooled in the center of an incised star.

then cut or scrape away the enclosed area. Glaze the entire piece with a light colored glaze and then, with a brush or medicine dropper, place a glob of the jewel glaze in the center of the cut-out star. During the firing the jewel glaze will flow, spreading out toward the points of the star. It will probably require some experimentation to determine just how much of the jewel glaze to apply and how deep to cut the star but, with practice, the results can be unusually attractive.

It is also possible to use jewel glazes or any glazes, for that matter in a more complex design, by employing separation walls. This is the reverse of the method of using incised lines to separate colored glazes that are not too fluid. While incised separation lines will prevent the average glazes from running into one another, they will not provide enough of a barrier for the extremely soft jewel glazes. For these glazes a wall is necessary. Therefore you must cut out the areas to be filled with glazes, leaving a raised line to act as a fence around each glaze. You may leave the raised lines bisque, or you can spray the entire piece with a light coat of clear glaze, either before or after applying the colored glazes. If you are interested in making more than one of these pieces, you can make the separation walls in the mold (see Chapter X), thus saving a great deal of time and work.

Keywords: Ceramic Decorations, Ceramics Decor, Ceramics, Painting

A decoration that is painted with under-glaze colors on top of an unfired opaque glaze is referred to as a Majolica decoration. The term “Majolica” originated many hundreds of years ago. During those early centuries most of the available clay was of a dark color which made decorating with brilliant colors difficult. Gradually the eastern potters learned that tin added to a transparent glaze would render it opaque, but tin was scarce. About the year 1500, many potters from the east, especially the Moors, were carrying their ware to the island of Majorca, off the coast of Spain, and since Spain was rich in tin, before long the potters added tin to their transparent glaze, producing a hard white opaque glaze. With this glaze covering the dark body of the clay, bright colors could be used effectively. The new ware was given the name “Majolica” and became very popular when it was brought into Italy. It is still used widely as a means of decorating ceramics.

Although today we are fortunate in having a wide selection of white clay bodies to choose from, thus eliminating the necessity of resorting to Majolica as the only means of decorating with bright colors, Majolica decoration possesses a charm that makes it attractive to modern-day ceramists. The effect derived from painting with under-glazes on top of the unfired glaze is totally different from that of an orthodox under-glaze decoration and the procedure is necessarily different too.

First glaze the ceramic piece with a white opaque glaze. Painting over a coat of unfired glaze is difficult, so give the glazed piece a light coat of gum tragacanth before attempting further decorating. Do not use a pencil to sketch the design on the piece because the point is likely to mar the glaze. Instead, brush the design on with diluted India ink or vegetable dye which will burn out completely during the firing and will, in addition, provide good practice for the brush work in the final design. Underglaze colors painted on top of an unfired glaze do not entirely fuse with the glaze when fired and often appear dull in contrast to the glaze’s sheen. To remedy this, add a small amount of transparent glaze to the underglaze colors so they will fire properly and shine with the glaze. The quality of the brush work is most important in Majolica decoration and glycerin or mineral oil used instead of water will make brushing easier. Because of the rough surface of the unfired glaze, a dry brush technique can be used to good advantage. Keep your decorating direct and free and avoid overworking your strokes. If

Illustration 95
To begin a Majolica decoration, glaze the piece with white opaque glaze and coat it with gum tragacanth.

Illustration 96
You can brush on a partial background with diluted underglaze colors.

you get a chance examine the Majolica ware from Italy; you will notice that the charm of the ware is derived largely from the freshness and colorful crispness of the decoration.

Illustration 97
Sketch the design on the piece with diluted India ink, which will burn out during the firing.

Illustration 98
Paint the design with dry brush strokes, a good technique to use on the rough surface of the unfired glaze. Make sure you have removed all excess color from the brush and do not go over your strokes or they will lose their effect.

Illustration 99
Add accents of black to complete the decoration, and fire.

Keywords: Ceramic Decorations, Ceramics Decor, Ceramics, Painting

Another way of painting with glazes is to place various glazes next to each other, separating them by incised lines. Covering the surface of the piece in this manner allows for great variation in textures, since matt glazes may be placed next to glossy glazes, textured glazes next to smooth glazes, etc. Try to arrange the decoration in such a way as to provide an interesting balance of textures as well as colors. Make good use of the many types of glazes: crackle glazes, matt glazes, speckled glazes, all can be combined with this technique. Avoid the use of very soft glazes, however, because even with the incised separation lines, a soft glaze may run into the lines and over into another glaze area. Another method using the soft or jewel glazes will be discussed later in this chapter.

Plan the design so that the separation lines form closed areas for the glazes. Work it out carefully on paper and transfer it to the green ware. Start incising the lines with a sgraffito tool, lightly at first and gradually cutting deeper. Do not cut too deeply because after you have applied the glazes you will have to scrape away any excess glazes that may have landed in the cut lines. When

Illustration 93
After firing, stain the piece with diluted liquid shoe polish. The stain will sink into the unglazed lines and into the crazing of a crackle glaze.

Illustration 94
The finished polychrome ash tray is well worth the time and trouble that went into the technique.

the separation lines have been incised, fill the enclosed areas with glazes.

Two applications of glaze are usually sufficient, three if you apply them lightly. Between applications go over the incised lines, scraping away any glaze that has spilled into them. You must keep the lines completely free of glaze if they are to act as separation lines. When the entire surface is covered with glazes and the separation lines are scraped clean, the piece is ready for firing.

After firing you may leave the lines as they are, or else you can rub a stain into them. For a stain, brush liquid shoe polish or India ink into the bisque lines, rubbing off the excess with a clean rag. It is best to dilute the stain, making several applications until the desired strength of color is obtained, because while it is an easy matter to wipe off the stain from the glazed areas, it is almost impossible to remove it from the bisque lines.

This technique is not used too frequently by ceramists, probably because it is time-consuming and requires a good deal of experimentation. But, for the decorator who is sincere in his efforts to create better ceramics, willing to devote the necessary time and not merely searching for the quick, easy way to decorate his ceramics, this technique is a rich and satisfying one and creates unusually handsome ceramics.

Keywords: Ceramic Decorations, Ceramics Decor, Ceramics, Painting