What Is The 9 Pottery Glazing Techniques?

Pottery glazing is the process of applying a glass-like coating to ceramic ware like plates, cups, vases and other objects made of clay in order to make them impermeable to liquids and give them an attractive finished surface. There are many different glazing techniques that can be used to decorate and add color to pottery. This article will provide an overview of 9 common glazing techniques used in pottery and ceramics.

The 9 pottery glazing techniques we will cover are:

• Underglaze
• Overglaze
• Majolica Glaze
• Raku Glaze
• Luster Glaze
• Crystalline Glaze
• Sgraffito
• Slip Trailing

Each technique provides a unique way to customize the look and feel of ceramic pieces. Glazing can serve both decorative and functional purposes for pottery. When applied correctly, glazes make pottery waterproof and suitable for holding food and drinks. The glazing process dates back thousands of years and continues to evolve as artists experiment with new styles and effects.

Underglaze

Underglaze is a colored decorative coating that is applied to bisqueware or greenware pottery before it is fired. It is made from a mixture of frit, ceramic stains, and binders. Underglaze comes in a variety of colors and allows potters to add intricate designs and patterns to their pieces before the final glaze firing.

Underglaze can be used on either bisqueware (first fired clay) or greenware (unfired clay). On bisqueware, the colors will appear more vibrant. On greenware, the underglaze will blend into the clay body for a subtle, misty look. Underglaze is typically applied with a brush, sponge, or pencil.

To apply underglaze, the potter starts by securing the bisqueware or greenware piece to the wheel with batting or a chuck. The underglaze color is loaded onto the brush and applied in smooth, even strokes following the intended design. Multiple colors can be layered to blend or outline shapes. Once the underglaze is completely dry, a final transparent glaze is applied overtop and the entire piece is fired to maturity.

During firing, the underglaze bonds with the glaze layer to become permanent. The underglaze provides beautiful colored accents under the glaze. Popular techniques like sgraffito involve scratching through the underglaze to reveal clay color underneath. Underglaze brings vibrancy and design options to finished ceramic pieces.

Sources:
https://www.soulceramics.com/pages/what-is-underglaze
https://www.thesprucecrafts.com/when-to-underglaze-pottery-2746192

Overglaze

Overglaze is a type of ceramic decoration applied on top of an already fired glaze. According to the Digitalfire Glossary, “Overglaze decoration means painting with colored glazes over the top of the high-fired glaze. It is then returned to the kiln so the additional glaze can mature” (https://digitalfire.com/glossary/overglaze).

Overglaze is considered a secondary process in ceramic decoration. The pottery piece is fired once to maturity to harden the clay body and fuse the underglaze. Then overglaze is applied on top and fired again at a lower temperature. This allows the overglaze to melt and bond without re-melting the underlying glaze layer.

Overglaze is commonly used for brightly colored decorations and intricate details that cannot withstand the high temperatures of primary glaze firing. It provides vibrant hues and eye-catching accents. Overglaze also allows for greater control and precision compared to underglaze techniques. Artists can paint finely detailed designs in thin layers of overglaze.

Overglaze is typically applied by brush but can also be airbrushed or screen printed. It comes in various formulas suited for different firing temperatures and surfaces. Popular overglaze techniques includemajolica, china painting and decals. With proper application, overglaze can create stunning decorative effects on ceramic wares.

Majolica Glaze

Majolica glazing is a technique that originated during the Renaissance in Italy and Spain. The term “majolica” comes from the Spanish island of Mallorca, which was an early production center of this type of pottery. Majolica glazes create a colorful, painterly look on pottery. The magic of majolica: How to create vibrant painterly decoration on pottery.

The majolica glazing process typically involves applying opaque colored glazes over a terra sigillata base. Terra sigillata is a refined white or tinted clay slip that produces a smooth, non-porous surface. The majolica colors are bold and bright, often applied with brush strokes to create decorative patterns and designs. Majolica glazes require high temperatures – cone 018-04 – to mature and fuse properly.

Raku Glaze

Raku glazing is a specialized technique associated with Japanese raku pottery. Raku refers to a style of quick-fired pottery first developed in Japan in the late 16th century. The raku firing and glazing process involves removing the pottery from the hot kiln after firing and placing it into containers with combustible materials like sawdust or leaves. This causes dramatic effects as the materials ignite and produce patterns of crackles, spots, or metallic lusters on the pottery surface.

To prepare for raku glazing, potters apply glazes with special formulas that react to the quick changes in temperature and atmosphere during the raku firing process. Common raku glazes include copper carbonate or red iron oxide, which produce metallic blues, greens, reds and coppery colors. A celadon raku glaze made from wood ash can also produce crackle effects. The raku pottery is bisque fired before the raku glaze is applied.

During the raku firing, the pottery follows a quick climb to around 1800-1900°F. It is then removed from the kiln using long metal tongs and placed into a container with sawdust or leaves. The combustible materials ignite from the heat, producing effects on the glazed surface. The pieces are then placed into a tub of water to stop the cracking process. Raku glazing involves unpredictability, as potters embrace the serendipitous effects of the firing process on the specially formulated raku glazes.

Sources: https://thepotterywheel.com/how-to-glaze-raku-pottery/, https://thepotterywheel.com/category/glazing-decorating/page/3/

Luster Glaze

Luster glaze is an overglaze made of finely ground metal particles like gold, silver, platinum, or pearl that create an iridescent metallic shine on pottery (https://ceramicartsnetwork.org/daily/article/How-to-Use-Ceramic-Luster-Glaze). It is applied over an already fired glazed piece and requires an additional third firing at a low temperature, usually around 1300-1400°F. The low firing helps the luster bond to the glaze and keeps the metal particles from burning off. Luster glazes are usually applied with a brush in detailed patterns and designs. The metallic oxides in the glaze melt during firing, leaving a thin translucent film of metal on the surface. This gives pottery a beautiful glowing sheen. Popular colors include gold, silver, copper, red, and rainbow. When fired correctly, luster glazes produce a bright, shiny metal finish.

Crystalline Glaze

Crystalline glazing is a type of glazing technique that results in a shiny, glass-like surface with visible crystal formations. It was developed in the 1980s and has become popular for creating visually striking ceramic pieces.

To create a crystalline glaze, potters mix zinc oxide, silica, and other ingredients like titanium dioxide and calcium carbonate into the glaze recipe. The glaze is applied to bisqueware and fired to around 2,300 degrees Fahrenheit. As the glaze melts in the kiln, it recrystallizes as it cools, forming the visible crystalline structures.

Factors like the clay body, glaze ingredients, and firing temperature all affect the final crystalline glaze effect. Controlling the cooling rate, known as “thermal shock,” also determines the crystal size and shape. Faster cooling results in smaller crystals. The glaze can be clear, opaque, or colored depending on the oxides used.

According to The Art of Crystalline Glazing: Basic Techniques, crystalline glazing requires careful testing and firing to achieve the desired results. When done successfully, the technique can create beautiful shimmering, cracking, and three-dimensional crystal effects on pottery.

Sgraffito

Sgraffito is a glazing technique that involves scratching through one layer of glaze to reveal the color underneath. It comes from the Italian word “sgraffiare” meaning “to scratch”. The process starts with applying a base coat of glaze over the bare clay. Once the base coat has dried to a leather-hard state, a contrasting glaze is applied on top. The top layer of glaze is then scratched through to create a decorative pattern and reveal the base color beneath. Common tools used for sgraffito include sticks, combs, needles, and ceramic scribing tools. Intricate, lace-like designs can be achieved. The scratching is done before any firing, so the glazes must be compatible in terms of temperature requirements and coefficients of expansion. Sgraffito allows potters to create bold, graphic designs by utilizing color contrast between layers. It’s an accessible, direct glazing technique for both functional ware and artistic expression.

Source: https://www.pinterest.com/marycampbell568/art/

Slip Trailing

Slip trailing is a decorative pottery glazing technique where liquid clay, known as slip, is applied on top of an unfired clay surface to create patterns and designs. The slip has a similar consistency to heavy cream or house paint. It is made from mixing powdered clay with water to produce a smooth, pourable liquid clay mixture.

To create slip trailing designs, the liquid slip is poured through a bottle specifically designed for slip trailing. These bottles have metal tips andapointed end for precise pouring and drawing. The artist carefully pours the slip from the bottle as they move it across the clay surface to “draw” the desired patterns and images. Things like flowers, animals, geometrical shapes, and intricate line work can be made with slip trailing.

The slip will show up as a raised texture on the clay surface after it is poured. When fired in a kiln, the areas with slip will take on a different color than the bare clay background.The contrast in colors between the textured slip design and clean surface makes the pattern stand out. Slip trailing results in beautiful, one-of-a-kind ceramic pieces.

It takes skill and a steady hand to master slip trailing and create intricate designs. But it is an accessible and fun way for potters and ceramic artists to decorate their clay work.

Conclusion

In summary, there are various glazing techniques that can be used to create beautiful and unique finishes on pottery. Underglaze, overglaze, majolica glaze, raku glaze, luster glaze, crystalline glaze, sgraffito, and slip trailing are nine key techniques potters use. Each one provides its own aesthetic effects through the manipulation of colored glazes, materials, firing methods, and more. While challenging at times, mastering these techniques allows potters to expand their skills and make one-of-a-kind works of art.