Archive for the 'ceramics' Category

The ceramist will find applying enamels quite different from ceramic colors since enamels (with the exception of the over-glazes) are not mixed and painted on with a brush in the usual way.

One way to apply enamels is to dust or sift the dry color. The clean copper piece is first given a coat of gum tragacanth or the special preparation, applied with a brush or sprayed with an atomizer. This will hold the fine particles of enamel in place. Then a base coat of transparent or opaque enamel is sifted on the piece through an 80 mesh wire screen (a piece of nylon stocking can be used instead or you can obtain from enamel dealers and manufacturers special jar lids that are already fitted with a small piece of 80 mesh screen). Before dusting on the enamel, place a clean sheet of paper under the piece to catch the excess enamel so that it can be returned to the jar.

When you are certain that the piece has been well covered, shake off the excess enamel by tapping the piece on its side. With most transparent enamels, especially the brown, yellow and beige shades, one thin coat is usually sufficient as a heavy coat will destroy the transparency. However, the transparent greens and blues, because they are affected by the warm copper tone, generally require a heavier application or a second coat to achieve the full intensity of color. With the opaque enamels you may find it necessary after firing the first coat to apply a second coat; opaque reds in particular, when applied directly on copper, tend to burn out and a clear red can seldom be achieved with one coat.

Another way to apply enamels is to inlay the wet colors, a method referred to as wet charging. This can be done directly on the copper or over a fired coat of flux (clear transparent enamel), which is actually more satisfactory. The advantage of the wet charge method is that transparent enamels can be placed next to opaque enamels and it is also the best way to execute a design consisting of

Illustration 145
The copper tie bars are decorated with wet charge on a fired enamel base coat.

complex shapes and numerous color areas. For the inlaying method, a small amount of gum is added to the dry enamel until a thick paste is formed. Do not allow the paste to become too fluid or it will be difficult to control. With a spatula or brush, place the enamel in position on the copper piece and push the wet enamel into the desired shape (a fine brush is excellent for pushing the enamel). Level the enamel with a spreader or brush and inlay the next color, continuing the procedure until the entire surface is covered and the color areas joined. Tap the piece gently on the side to level the enamels.

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Preparing the copper

Although silver and steel are also used for enameling, copper is by far the most practical metal. The all-important factor in the

Illustration 144
To clean copper, immerse it in an acid solution with tongs.

preparation of the copper is cleanliness, for the enamel will not adhere to a metal surface on which there is the slightest trace of grease or dirt.

There are several methods that can be used to clean the copper, one of which is the acid bath. The usual acid solution consists of one part nitric acid added to five parts water. Be sure to add the acid to the water. Never add water to acid or a violent chemical reaction will result, causing serious burns to anything with which the acid solution conies in contact. When preparing the solution, place the water in a glass dish and slowly add the nitric acid. Immerse the copper piece in the solution with tongs and remove the piece when the copper is a clean, pink color. Rinse and dry the copper immediately. Test the copper for cleanliness by running water over it. If the water does not form beads, the copper is ready to be enameled.

If it is not practical to work with acids, other methods may be used. One way to clean the copper without using an acid bath is by means of a commercial preparation which is a non-hazardous granular compound that is mixed with water. The copper piece is placed in the solution until clean. Another way to clean the copper is to rub the surface with steel wool and scouring powder or a clean rag that has been soaked in vinegar and dipped in salt.

While any of the foregoing methods are satisfactory and are the generally accepted cleaning methods, some arts and crafts stores now have a specially prepared gum solution that can be used instead. With it no cleaning is necessary except a polishing of the copper with steel wool or a copper cleaner to remove oxidation stains. You apply the preparation to the polished copper surface with a brush and it acts as a cleaning agent and also as the adhesive for dusting on the enamel. It can be used only when a coat of enamel is to be dusted on, not when a wet charge method is used.

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Copper enameling

Have you ever thought of exploring another fascinating field closely allied to ceramics, that of copper enameling? Since enamels and ceramic glazes are both a form of glass and both are fired at high temperatures in a kiln, it is not surprising that so many ceramists include enameling in their ceramic activities. Naturally we do not intend to cover the entire field of copper enameling in one chapter, but it is hoped that the information offered here may inspire you to pursue the subject further.

Types of enamels

Glass enamels are generally purchased in ground form. When applied to metal and heated they fuse to a glassy coating, much like a ceramic glaze. There are four types of enamels available to the enamelist: opaque, transparent, opalescent, and overglaze enamels. Opaque enamels are solid colors through which light will not pass; transparent enamels permit the surface of the metal to be seen through the colors; opalescent enamels are transparents with a milky appearance; and the overglazes are used for detail work over an enameled surface. For general purposes, the opaque and transparent enamels are quite adequate and provide the enamelist with a wide range of colors and effects.

One of the main differences between enamels and ceramic glazes is that the enamels cannot be mixed to produce new shades of color. Unfortunately, when two enamels are mixed the tiny grains of each color will show up as specks rather than as a smooth new color. For this reason, the enamelist requires a large palette of colors.

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Colored glazes

The simplest and often the most effective way of decorating jewelry is with colored glazes. They provide a richness and depth of color difficult to attain in any other way. Pieces containing an incised or imprinted design and pieces with modeling details should always be decorated with one or more colored glazes to bring out the full effect of the surface design. Such pieces often require only a single colored glaze (fairly soft) which will run off the high points and sink into the recessed areas. Incised pieces may also be attractively decorated with a coat of white opaque glaze over which is applied a soft, colored, transparent glaze. Such an interesting mottled effect results from this double glaze treatment that it need not be restricted to incised pieces but can be used with equal effectiveness on pieces containing no surface decoration.

Jewel glazes can be used on almost any type of piece and are excellent for jewelry because of their brilliance and depth of color. Small chunks of colored glass placed on top of a colored glaze will also produce a jewel effect.

Gold on jewelry

A few touches of gold will enrich most jewelry pieces, but they must be applied sparingly in order not to cheapen the piece. The gold may be used as an entire line design if the lines are few and the design simple. Or it may be used as an accent, or in the form of marbelizing, a decoration that is excellent for jewelry, especially on a background of colored glazes.

For an interesting gold Variation, try “gold jewels.” Simply scoop out one or more circles about Vs of an inch deep in the green ware (a drill bit can be used for this purpose), decorate, glaze and fire the ware as usual. Then fill each incised circle on the fired piece with a glob of gold and fire the piece at the usual gold firing temperature. The small recessed areas of gold catch the light in such a way that they resemble sparkling jewels.

Jewelry findings

The pin backs, earring backs, etc., for jewelry are referred to as findings and may be obtained at craft and ceramic stores. These findings can be cemented to the back of the ceramic piece with liquid cement, and it is a good idea, when glazing your jewelry, to leave the back unglazed so that the finding will adhere more easily to the piece.

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Underglaze decoration

Underglaze decoration is most effective on flat, simple pieces of jewelry where color and design are needed to lend interest to a conventional shape. The underglaze designs can be of any type: modern, traditional, geometric, abstract, amusing. The style is not too important, but it is important to keep in mind that on small pieces of jewelry the design should consist of fairly large, simple areas with a minimum of fussy details. Although the design may be composed of many colors, these should be arranged in such a way that there is always a focal point of design interest or a definite color pattern that will carry well on a small piece of jewelry.

Stencils or masks are attractive on small pieces of jewelry but, because of size restrictions, they too should be kept very simple. Fish, leaves, geometric shapes and stylized flowers can be used effectively as stencil motifs, with a few bold accents of color or sgraffito added to vitalize the stenciled appearance.

A sprayed background consisting of a light color with an edging of a darker color

Illustration 140
A sgraffito design on an underglaze background makes an unusual piece.

Illustration 141
Sponging provides the background for a geometric design.

Illustration 142
A freely-executed design has a sponged edging.

Illustration 143
Jewel glazes, because of their brilliance and depth of color, are excellent for jewelry. They may
be applied to almost any type of piece.

can be used as a complete decoration for a more complex shape since the dark edging tends to act as a frame outlining the form. Or it can be used as a background for a line design in underglaze color, sgraffito or gold.

A more intricate type of decorating, striking in effect, is possible with geometric designs rendered in blacks, whites and a few bright colors. Indian designs also lend themselves to this type of decoration and when done in simple color schemes such as black, white, brown and turquoise, they are quite stunning on jewelry. Remember that designs of this type are best suited to simple shapes.

Another underglaze decoration that is particularly well suited to jewelry is a simulated mosaic design. A real mosaic, of course, consists of many small pieces of ceramic tile arranged in a design and cemented permanently in place. However, much the same effect can be obtained with underglaze colors and sgraffito lines. A mosaic-like design (that is, a design broken up into many small irregular areas) is scratched on the piece with a sgraffito tool. On jewelry, do not make the areas too small or too numerous or the design will become so jumbled that it will not carry at all on a small piece. The areas within the scratched lines are then painted with underglaze colors and the entire piece is glazed with a clear glaze. The sgraffito lines may be left white or they may be filled with a dark underglaze color prior to glazing.

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Press molds

Small press molds with which to make jewelry pieces can be purchased from your ceramic dealer or mold manufacturer, These

Illustration 138

136. For added interest, incise the beads with a modeling tool.
137. String the beads on a piece of nichrome wire.
138. Fasten the wire ends in clay pyramids and fire.

molds are available in an infinite variety of shapes appropriate for jewelry. You may also make your own press molds (see Chapter III) over such small objects as buttons or coins.

Surface decoration

Simple jewelry pieces, especially those to be decorated with colored glazes, will be greatly enhanced by some type of surface decoration. This may be in the form of an incised design, which can be made with a pointed tool after the piece has been formed, or it may be a textured pattern. Still another type of surface decoration is possible by imprinting designs into the wet clay with coins, costume jewelry, or any object containing a fairly definite raised design. Remember that the clay must be wet for an imprinted decoration.

A very unusual surface decoration can be achieved by the use of colored grog in a press mold. You can color with any underglaze color by pouring the liquid underglaze into the grog and allowing it to dry. When

Illustration 139
Underglaze decoration enhances flat, simple jewelry pieces. This Indian design was executed in black, brown and turquoise.

the grog (now colored) is dry, sprinkle it in the press mold and press the clay into the mold. If more than one color is used, the clay piece will have an almost mosaic-like effect.

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Jewelry, whether fashioned from precious metals and stones or wrought from clay and
glazes, has been a constant source of inspiration to every craftsman throughout every age in history. In the field of ceramics the opportunities are unlimited. The varied and interesting forms you can create combined with the jewel-like colors you can attain make ceramics a natural and practical medium for jewelry.

The studio ceramist can, at no great expense, apply his ceramic knowledge and talents to the fascinating project of making individual jewelry for his own pleasure or on a small business scale. The purpose of this chapter is largely to offer suggestions on how the various methods and techniques that have been discussed in previous chapters can be adapted to ceramic jewelry in particular.

Forming jewelry shapes by hand

There are so many shapes you can make into jewelry that it would be difficult to imagine one that would not be appropriate. Stars, leaves, butterflies, flowers, fish, free-form shapes all these and many more you can form by hand into flat pieces (to be incised or painted) or fully modeled pieces. Flat pieces may be cut out of plastic clay by rolling out a slab of clay to the desired thickness, sketching in the outline of the shape and then cutting it out with a knife. The edges should be smoothed and rounded and any incised decorations should be done while the clay is in a leather hard condition.

On flat pieces of this type, underglaze decorations are usually very effective and give a great deal of interest and color. Cookie cutters can also be used to form conventional flat shapes, such as circles, diamonds and hearts, but these too require a certain amount of finishing by smoothing and rounding the edges and they definitely will need an interesting decoration, even more so than less conventional shapes. Any scraps of dry greenware that you may have can be used for flat jewelry. The clay will be too dry to cut with a knife without chipping, so use a jeweler’s saw or a spiral hacksaw blade to form the pieces. (See Appendix.)

Ceramic beads are fun to make. You can cut small pieces from a slab of plastic clay and fold them into various shapes. Or you can cut slices from a rolled coil of clay. With simple round or cylindrical beads you may find it necessary, from a decorative point of view, to incise a design in the beads, since the shape is not too interesting in itself. As soon as the beads have been formed, string them on a piece of nichrome wire, the ends of which can be fastened in two mounds of clay, and bisque fire for safer handling. Bisque fire about 400 under the maturing temperature so that the pieces will be porous enough to absorb the glaze afterward. Otherwise, the glaze may tend to run off the high spots. After the beads have been

Illustration 135
To make ceramic beads, first slice a rolled coil of clay with a sharp knife.

Illustration 136

Illustration 137

bisque fired, they may be decorated with underglaze colors and glazed, or decorated with colored glazes actually the simplest and most effective means of decoration for such small pieces. The glazed beads are then strung again on the nichrome wire and glaze fired.

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Some very unusual effects can be achieved by means of gold marbelizing. Put a drop or two of gold into a container of water and stir the mixture lightly. Since the gold is not soluble in -water, it will not mix with the water but will float on the surface in streaks. Dip the glazed piece in the marbelizing mixture, removing it when the gold has become as evenly distributed as possible on the piece.

The simplest background for this technique is clear glazed white ware. It is very effective since white and gold are always pleasing together. However, richer and more interesting effects are possible by using colored glazes as a background for the gold marbelizing. There are so many colored glazes that produce exciting results when combined with the marbelizing technique that this provides a good opportunity to experiment. In places where the gold has touched the glazed surface very lightly, the annoying purplish stains may appear when the piece is fired. Although these stains are ordinarily objectionable on gold decorated ware, on mar-belized pieces the faint areas of purple are often extremely attractive. This is particularly true if the background glaze is a turquoise or light blue, in which case the purple stains blend with the blue and gold, producing quite beautiful sea-like effects.

Firing overglaze colors and gold

While overglaze colors and gold are applied somewhat differently, their maturing temperatures are the same and both are fired at 1150 -1250 , The firing should begin slowly, as with all ceramic firing. Start the kiln on Low, leaving the door open to allow the oil in the colors to burn out. In half an hour turn the kiln to Medium, with the door still open. You will notice a peculiar, rather acrid odor coming from the ware, especially gold decorated ware, which is merely the oil burning out of the colors. After the kiln has been on Medium for half an hour, turn it to High, but do not close the door yet. In about another half an hour or when the inside of the kiln is nearly cherry-red in color, close the kiln door. If you have a pyrometer you will know that this “oil smoking” period is over when the temperature reaches about 450 -550 . Then you can close the kiln completely. Leave the kiln on High with the door closed, until the maturing temperature is reached.

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Gold

Although gold is an overglaze color, it is mentioned separately because of its special characteristics. Gold can be purchased in liquid form at any ceramic store and is available in various shades-Bronze Gold, Roman Gold, Bright Gold, etc. For general purposes, Bright Gold is the most widely used. At first glance, gold might appear to be quite expensive, but a very small bottle of gold will last a long time since it is not ordinarily applied to large areas and does not require more than one coat.

There are several precautions you should take when decorating with gold. First of all, make certain that the glazed piece is absolutely free of dust because even the most minute particle of dust will cause trouble. Any foreign material must be kept away from the gold. For this reason, it is a good idea to reserve a special brush for gold decorating and to set aside a separate place for gold work, away from the rest of your ceramic work. This will help to maintain the absolute cleanliness necessary when working with gold.

Applying gold

Liquid gold as it comes from the bottle is usually the right consistency for decorating, but if it is necessary to thin the gold, do not use turpentine. Instead, use a preparation called Essence of Gold or Gold Essence. Use this to clean your brushes as well. The gold must be thin enough to be workable but if it starts to spread it has been diluted too much. A correct application of gold will appear brown before firing, but it will fire to its proper metallic luster. Too faint an application will fire purple. Do not go over the painted area in an attempt to smooth out the brush strokes, as they will flow together in the firing and become nonexistent. It is helpful to keep a

Illustration 134
Sponging is combined with brushwork in the tile. When sponging with overglaze colors, pat the sponge very gently.

small glazed dish or tile on which to experiment with your brush strokes before you start the actual decorating.

Be very careful to keep the gold on the brush or in the bottle and not on your fingers. This is extremely important because the slightest smudge of gold on the glazed surface will turn a surprising purple when fired.

If you make mistakes, don’t try to remove them singly, but wipe off the entire gold decoration with turpentine and start again. Go over the surface several times with turpentine and a clean rag, making certain that every bit of gold has been removed. Otherwise, you may discover those pretty but unwanted purplish stains on your fired piece.

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Mixing overglaze colors

Overglaze colors may be purchased in liquid form ready for use or in powdered form that must be mixed. If you buy the overglaze colors in dry form, mix them with fat oil and turpentine. Any hard, smooth surface can be used as a mixing ground (glazed tiles, plates or a sheet of glass provide satisfactory surfaces on which to mix your colors). Place a small amount of dry color on the mixing surface and add fat oil, a few drops at a time, until the color can be mixed into a paste with a palette knife (a flexible artist’s knife used for oil painting and available at any art store). Add enough turpentine to the paste to render the color workable with a brush.

Applying overglaze colors

The main thing to remember when applying overglaze colors is that these colors cannot be worked over. Once the color is down, it should stay or be completely wiped off if a mistake has been made. Because the overglaze colors are applied on a glazed surface which is non-porous, the colors do not sink into the piece as underglaze colors do on green ware, but stay on the surface. Thus, if you attempt to pile color on top of color you may find that you are taking off the underneath color instead. The safest way to apply one overglaze color over another or to apply a second coat of the same color is to fire the piece after the first coat of color has been applied. Then the second coat or second color can be painted without damage to the color underneath. Each color should be fired before another is applied over it. This can become a rather involved process if you plan to do a very intricate decoration. However, for fairly simple decorations that require little or no shading or complicated color

Illustration 133
A light, fresh feeling is achieved in this overglaze decoration. (Courtesy of Florence Cox.)

values, it is possible to paint one color over another if you allow the first color to dry completely. You must take great care not to exert too much pressure on the brush as this will drag off the underneath color. Apply the second color as lightly as possible and confine it to small areas.

Although brushwork is the primary technique used in overglaze decoration, it is possible to combine a few of the other ceramic techniques with over glazes. Sponging can be used nicely, especially where shading is desired. The only difference in the technique when applied to overglaze decoration is that the sponge must be cleaned with turpentine instead of water and here again you must be very careful to pat the sponge gently when applying color over another unfired color. Sgraffito can also be used to a small extent in overglaze decoration. The color must be thoroughly dry before any cutting is attempted and the sgraffito should be limited to simple accents rather than a complicated line design since the sgraffito tool is inclined to slip and slide on the smooth glazed surface. If you make small mistakes and cannot wipe them off without ruining the entire decoration, you can scratch them off after the color is dry.

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