What Does Under Glazed Mean?

Definition of Underglaze

Underglaze is a type of ceramic decoration applied to pottery and ceramics before firing and glazing. According to
Merriam-Webster
, underglaze refers to “a ceramic decoration applied to pottery before glazing and firing.” It consists of mineral pigments suspended in a liquid medium that is painted onto the unfired clay. When the pottery is fired at high temperatures, the underglaze fuses with the clay body to create a permanent colored design under the glaze.

Unlike glazes which create a glassy coating, underglazes are designed to be absorbed into the clay so the color becomes part of the body of the ceramic after firing. Once the piece has been decorated with underglaze, a transparent glaze is applied overtop and the entire piece is fired again to melt and fuse the glaze. This protects the underglaze art while allowing the colors underneath to remain visible.

In summary, underglazing is a key technique in ceramic decoration and involves applying pigments before firing and glazing to integrate color into the clay body itself.

Underglaze vs Glaze

Underglaze is a type of ceramic decoration that is applied to pottery or ceramic pieces before firing. Glaze, on the other hand, is applied after the initial bisque firing. This key difference distinguishes between the two decorative materials.

Underglazes are composed of pigments suspended in a flux base that allow the colors to adhere to the unfired clay surface. Common types of underglaze include underglaze pencils, underglaze paints, and underglaze inks. Underglazes are absorbed into the porous bisque clay body when applied. After underglazing, the pottery must be fired to a high enough temperature to mature the underglaze and permanently affix it to the clay. Typical firing temperatures range from cone 04 to cone 6.

In comparison, glazes are glass-like coatings made of silica, fluxes, and colorants. They are applied after the initial bisque firing. The glaze melts during the glaze firing and coats the pottery piece with a smooth, glossy finish. Glazes make the pottery non-porous, waterproof, and suitable for utilitarian and food-safe ware. The underglaze decoration becomes sealed under the transparent glaze after firing.

While underglaze and glaze serve different roles in ceramic decoration, they work together to create beautiful, colorful pottery. Underglaze brings out intricate designs and patterns before firing, and glaze makes the ware functional and enhances the underglaze colors with a clear, shiny coating.

Types of Underglazes

There are a few main types of underglazes that are commonly used by ceramic artists and potters:

Commercial underglazes are manufactured underglaze products that can be purchased from art supply stores. These underglazes come in jars of liquid underglaze or sets of underglaze pencils and are known for their vibrant colors and ease of use. Popular brands of commercial underglazes include Amaco Velvet Underglazes, Duncan Underglazes, and Mayco Underglazes (https://www.kingstonceramicsstudio.com/post/the-underglaze-basics).

Homemade underglazes can also be created by mixing porcelain, frit, and stains. Homemade underglazes allow artists to customize colors and achieve effects not possible with commercial products. However, homemade underglazes require testing to achieve the right formulation (https://www.kness.fr/en/underglazes/).

Underglaze pencils and crayons are another common type of underglaze product used for drawing fine details and intricate designs. Colored underglaze pencils work similar to colored pencils on paper and are available in sets with a wide range of colors (https://www.kingstonceramicsstudio.com/post/the-underglaze-basics).

Underglaze Decorating Techniques

There are many creative ways to use underglazes to decorate pottery pieces. Some of the most common underglaze decorating techniques include:

Painting

Underglazes can be brushed or painted onto bisqueware similar to using acrylic paints. The underglaze paints come in a variety of colors and effects like metallic. Painting allows for freehand designs, patterns, images, and more. https://thepotterywheel.com/underglaze-techniques/

Printing

Underglazes can be applied using printmaking techniques. Items like leaves, lace, or stencils can be used to imprint designs. Sponges and stamps are also popular for printing underglaze decorations onto pottery.

Drawing

Underglaze pencils and crayons allow for hand-drawn artwork. The colors appear more vivid compared to using colored pencils. Drawings can be detailed pieces or quick doodles sketched onto bisqueware.

Sculpting

Sgraffito involves carving through underglaze to reveal the clay color underneath. Wax resist methods like batik can also be done. Inlaying colored underglaze into engraved clay is another sculpting technique for decoration.

Firing Underglazed Pottery

When firing underglazed pottery, it’s important to fire to the correct temperature range to properly melt and fuse the underglaze decoration to the clay body. Most underglazes are formulated to fire between cone 04 and cone 6 (The Underglaze Basics). Firing too low can result in the underglaze not bonding properly, while firing too high can burn out the underglaze colors.

It’s also crucial to apply a transparent glaze over the underglaze before firing to seal and protect the underglaze decoration. According to Pottery Crafters, underglazes are porous and will absorb moisture if not properly sealed with a glaze firing. The glaze creates a glassy surface that keeps the underglaze colors vibrant. Typically, the glaze should be fired to the same cone temperature as the underglaze for compatibility.

Test tiles are recommended to determine the ideal firing schedule for a particular clay body and underglaze combination. Pay close attention to the underglaze manufacturer’s firing recommendations as well. With the proper firings, underglazed pottery will have durable, beautiful colors.

Applying Glaze Over Underglaze

When applying glaze over underglaze, it’s important to choose a glaze that is compatible and won’t cause reactions. A clear glaze is typically recommended, as it will allow the vibrancy of the underglaze colors to show through. According to discussions on Reddit, many potters have success using Amaco’s CG918 Clear Brushing Glaze, which can be applied in multiple coats over underglaze decorations without obscuring the colors underneath (source).

In terms of application, 2-3 coats of a clear glaze are often advised to fully seal the underglaze colors and provide an even finish. It’s important not to apply the glaze too thickly over intricate underglaze details or textures, as this can cause blurring. Allow each coat to dry before adding the next. Some potters recommend gently wiping or brushing away excess glaze from detailed areas using a damp sponge or soft brush between coats for the best results.

Underglaze History

Underglaze originated in 9th century Persia during the Islamic Golden Age. Potter’s began experimenting with lustreware pottery by applying metallic glazes underneath a clear glaze. According to the Wikipedia article on Underglaze, this technique spread to Egypt and Syria and by the 13th century lustreware was popular across the Middle East.

The first recorded use of underglaze to decorate pottery dates back to 9th century Persia. Master potters discovered they could apply oxides onto unfired clay and cover it with a translucent glaze, creating colorful designs beneath the surface. This technique allowed for more intricate patterns and effects compared to just painting on top of glazed ceramics.

Underglazes became widely used across the Islamic world during the medieval period. Notably, potters in Turkey, Egypt and Syria were renowned for their mastery of “underglaze blue” decorative ware, often with plant and geometric motifs. The cobalt pigment used to make the deep blue color was highly prized. According to The History of Underglaze Blue, by the 10th century the technique had spread along trade routes to Spain and North Africa.

In the 13th century, Persian potters began using underglaze decoration not just for traditional earthenware but on porcelain as well. From the Near East, knowledge of underglaze spread to China and by the early 14th century underglaze blue became popular in Chinese porcelain. This demonstrated the versatility of underglaze for decorating many types of ceramic bodies.

Notable Underglaze Artists

Some of the most famous ceramic artists have become well-known for their mastery of underglaze decoration techniques. Underglaze allows artists to add color and intricate details before a clear glaze is applied over the top. Some notable underglaze artists include:

Terri Kern is an American ceramic artist known for her meticulous and highly detailed underglaze paintings of animals and nature scenes. She can spend over 1000 hours on a single piece, applying thousands of fine brushstrokes with underglaze (source).

Peter Voulkos was an influential American ceramic sculptor who helped bridge the gap between fine art and ceramics. He often incorporated underglazes in his abstract expressionist works to add splashes of color and texture (source).

Arlene Shechet is a contemporary American ceramic artist known for her complex and dynamic sculptural forms. She frequently uses underglazes and oxide washes under translucent glazes to create depth and interest (source).

Other influential ceramic artists who have worked extensively with underglazes include Bernard Leach, Shoji Hamada, Karen Karnes, and Maija Grotell. Their innovative underglaze techniques have inspired generations of ceramic artists.

Underglaze Tips and Tricks

When working with underglazes, there are some helpful tips to keep in mind for best results:

Application Tips:

• Underglazes can be applied to either bisqueware or greenware, but work best on bisque as the clay body has been fired and will absorb the underglaze more evenly. Applying to greenware can lead to blotching.
• Multiple thin layers of underglaze tend to give better results than one thick coat. Build up the layers slowly.
• A damp sponge can be used to softly blend and feather underglaze edges.
• Underglazes can be painted, splattered, sponged, airbrushed, or stamped on.
• Allow each layer of underglaze to dry fully before adding another layer.

Common Mistakes:

• Applying too thick of a coat which can lead to cracking or peeling.
• Not allowing proper drying time between layers.
• Using oil-based underglazes with water-based glazes. Always check for compatibility.
• Mixing multiple underglaze brands.

Troubleshooting Tips:

• If underglaze is not adhering well, scuff up the bisque surface first before applying.
• Wipe off underglaze with a damp sponge and reapply thinner layers if heavy cracking occurs.
• Use a compatible clear glaze over the top to provide an impermeable surface and bring out the underglaze colors.

Following proper underglaze application techniques will help avoid common mistakes and lead to beautiful, vibrant results. Experiment, practice layering, and allow for plenty of drying time. With a bit of care, underglazes can create stunning ceramic effects.

Underglaze Recap

Underglaze is a ceramic decorating material that is applied to bisqueware pottery or greenware before being covered with a transparent glaze and fired in a kiln. It allows for intricate decorative effects under the glaze.

The key differences between underglazes and glazes are that underglazes are opaque, non-fluxing, and require a protective glaze coating when fired. Glazes are translucent to transparent and flux during firing to create a glass-like coating.

There are many types of underglazes available including colored underglazes, underglaze pencils, terra sigillatas, engobes, and china paints. Each has unique decorative qualities.

Underglazes can be applied using a variety of techniques such as brushing, dipping, pouring, sponging, stamping, and more. After bisque firing or greenware stage, the underglaze design is permanent so the pottery can be safely handled before glazing.

When firing underglazed pottery, it’s important to follow the manufacturer’s instructions for firing temperature and glaze compatibility. Typically, underglazes fire between cone 04-6. The glaze must mature at the same temperature as the underglaze for optimum results.

Underglazing has a long history dating back thousands of years. Many cultures have used it to create ornate, colorful pottery. It remains popular among ceramic artists today as an versatile, accessible decorating medium.

With some basic knowledge, underglazes can be used by all levels of potters to add beautiful, creative touches to pottery and ceramic art. Their versatility, affordability and easy application make them a great choice for hand decoration.