What Is Under Glaze Used For?
What is Underglaze?
Underglaze is a decorative material used in pottery and ceramics before the final glazing and firing process. It consists of ceramic materials such as clay, flux, and colorants that allow it to adhere to the unfinished ceramic surface. The purpose of underglaze is to add colored designs and patterns before covering the pottery with a transparent glaze.
According to the Wikipedia definition, “Underglaze is a method of decorating pottery in which painted decoration is applied to the surface before it is covered with a transparent ceramic glaze and fired.” [1] The painted underglaze designs fuse with the surface during firing and show through the transparent glaze layer after firing.
Underglazes can be used to hand-paint complex designs, apply solid colors, create patterns like stripes or dots, or resist areas before glazing. The colors remain vibrant even after firing since the glaze protects the decoration. Underglaze allows more creativity in surface decoration than glazing alone.
Types of Underglazes
There are two main categories of underglazes commercially available – liquid and powdered. Liquid underglazes are premixed, ready to use straight from the bottle with a brush or dipping. They provide intense, opaque colors. Popular brands of liquid underglaze include AMACO Velvet Underglazes, Mayco Underglazes, and Duncan Underglazes (Source). Powdered underglazes must be mixed with water before use. They produce a more translucent effect. Leading brands of powdered underglaze are Mason Stains and Amaco Underglaze (Source).
In addition to commercial underglazes, potters can make their own homemade underglazes. These are generally made by mixing metal oxide pigments with a medium like gum arabic or methyl cellulose. Common homemade underglazes include velvet underglazes made with gum arabic and porcelain pigments, wax resist made by painting wax on bare clay, and colored engobes which are pigmented slips. Homemade underglazes allow for custom colors and effects (Source).
Uses and Techniques
The main use of underglaze is decorative – it adds color and design to pottery before the final glazing and firing process. Underglaze can be applied to bisqueware or greenware using a variety of techniques including:
Painting – Underglaze can be brushed or painted onto the pottery piece allowing for intricate designs and effects. The velvety consistency of underglaze makes it ideal for painting fine details and patterns.
Dipping – Entire pottery pieces can be dipped into underglaze to evenly coat the bisqueware with color. This is one of the more traditional underglaze techniques according to this article on underglaze techniques.
Sponging – Using a sponge, underglaze can be dabbed onto the pottery piece to create mottled or textured effects.
Splattering – Flicking a brush loaded with underglaze creates interesting splattered patterns.
Unlike glazes which result in glossy finishes, underglaze allows for matte, opaque colors. It also enables more intricate and detailed designs not possible with regular glazing techniques. However, underglaze must be covered with a transparent glaze before firing the pottery in a kiln according to this article on underglaze techniques.
Advantages of Underglazes
Underglazes offer many advantages for ceramic artists. One key benefit is the wide range of colors and effects available with underglazes. They come in a broad spectrum of colors, ranging from vibrant primaries to pastel tones. Underglazes also allow artists to achieve unique special effects like crackle, metallic, and iridescent finishes.
Another advantage is that underglazes can be applied to raw clay before the first firing, unlike glazes which require an initial bisque firing. This allows the artist to skip a firing and save time. It also enables underglaze colors to integrate into the clay body for a more unified effect.
Underglazes also provide more precision and control compared to liquid glazes. Their thick consistency allows artists to paint fine details and intricate designs not possible with thinner glazes that run and bleed. Underglazes can be painted, airbrushed, stenciled, screen printed, and more for maximum versatility.
Additionally, underglazes require lower firing temperatures, typically cone 06-04 versus higher temperatures for glazes. This makes underglazes ideal for low-fire clays and saves energy costs. It also reduces the risk of over-firing and distortion.
Finally, underglazes allow artists to layer colors and textures in ways not possible with glazes alone. Multiple layers of underglaze can be built up to create dimensional effects. And underglazes are available in complementary translucent shades designed to overlay without muddying.
Sources:
https://www.soulceramics.com/pages/what-is-underglaze
https://www.thesprucecrafts.com/when-to-underglaze-pottery-2746192
Limitations of Underglazes
While underglazes offer some advantages, they also come with certain limitations that ceramic artists should be aware of. One of the main limitations is that underglazes require a glaze to be applied on top before firing. According to Digital Fire, underglaze surfaces do not allow the passage of water to the same degree as bisque, so a glaze needs to be applied on top to create a glassy surface and allow gases to escape during firing. Without a protective glaze layer, underglazes can become marred or damaged.
Underglazes are also more fragile than overglazes. As Sue McLeod Ceramics explains, issues like glaze crawling or peeling can expose the bare underglazed clay and ruin designs. Extra care needs to be taken when applying glazes over underglazes to prevent problems.
In some cases, using underglazes requires multiple firings. The underglaze must be fired onto the bisque before applying the glaze and firing again. This extra step can add time and complexity compared to single-fire overglazing techniques. Underglazes also require a relatively thin application to prevent issues like color bleeding. Applying colors too thickly can lead to muddiness or blurring of the design.
Tips for Using Underglazes
When working with underglazes, it’s important to follow some best practices to achieve the best results. Here are some key tips to keep in mind:
Test colors and techniques on test tiles first. Underglazes can react differently depending on the clay body, so it’s important to test them out before applying them to your final piece. Test for compatibility with glazes as well.
Apply multiple thin layers rather than one thick layer. Underglazes achieve better color saturation when built up gradually. Let each layer dry fully before adding the next.
Clean off any excess underglaze from the tile surface before applying a glaze. Leftover underglaze can cause glaze defects.
Use wax resist or masking tape for sharp edges and crisp lines. The fluid nature of underglazes makes them prone to bleeding.
Allow underglazes to dry fully before firing or glazing. Insufficient drying can lead to pinholes, blistering, and other issues. Drying times vary based on climate, thickness of application, etc.
Be mindful of application technique. Underglazes can be brush painted, airbrushed, sponged, splattered, and more. Certain techniques like sponging will naturally create a mottled look.
Underglaze vs Overglaze
Underglaze and overglaze are two different decorative techniques used in pottery and ceramics. The main difference between them is when they are applied during the production process.
Underglaze is applied before the final firing and glazing of a ceramic piece. It is then covered by a transparent glaze and fused to the clay body during firing. Underglaze requires the glaze in order to bond with the clay. It becomes a permanent part of the pottery after firing.
Overglaze is applied after the final firing and glazing. It sits on top of an already fired glaze layer and does not fuse with the underlying glaze or clay body. Overglaze is not as durable as underglaze since it can wear or chip off over time.
The key differences are:
- Underglaze is applied before glaze and firing while overglaze is applied after firing
- Underglaze needs a glaze to fuse it to the clay while overglaze just sits on top unfused
- Underglaze is more durable and permanent compared to overglaze
Both underglaze and overglaze allow for creative decoration but underglaze becomes an integral part of the final pottery piece while overglaze is more temporary.
Notable Underglaze Artists
Underglazes have been used to decorate ceramic pieces for centuries by artisans around the world. Some notable artists who utilized underglaze techniques in their work include:
Clarice Cliff (1899-1972) was an English ceramic artist active in the 1920s and 30s. She was known for her innovative and vibrant Art Deco style pots and vessels with geometric and abstract underglaze designs. Her most famous pieces were made at the Bizarre pottery factory. [1]
William De Morgan (1839-1917) was a leading English ceramicist during the Arts and Crafts movement. He rediscovered the use of metallic luster overglazes and underglazes, creating vivid ceramics with intricate patterns and designs. The William De Morgan brand continues producing handmade pottery today. [2]
Josiah Wedgewood (1730-1795) was an English potter who industrialized ceramic manufacturing. He perfected underglaze transfer printing, allowing detailed decorative patterns to be efficiently applied to pottery on a large scale.
Maria Martinez (1887-1980) was a famous Native American potter from San Ildefonso Pueblo, New Mexico. She helped revive traditional Pueblo pottery styles including matte black pottery with polished avian and geometric underglaze designs.
Historically, Persian pottery featured intricate underglaze painted patterns and calligraphy dating back to 9th century Persia. The cobalt blue underglaze and lustrous glazes created a signature aesthetic still emulated today.
Innovations in Underglazes
Underglaze technology has rapidly advanced in recent years, with several key innovations improving the possibilities for ceramic artists. New underglaze formulas feature brighter, more vibrant colors than ever before. Specialty underglazes have also emerged, including crackle underglazes that create intriguing crackled effects, metallic underglazes with a lustrous sheen, and iridescent underglazes that shift colors depending on the viewing angle.
Underglaze pencils and markers now allow artists to draw fine details and textures directly onto bisqueware pieces with precision. Digital underglaze printing has also enabled new design capabilities, allowing artists to print complex custom images and patterns onto ceramic surfaces using underglaze inks.
As underglaze technology continues to progress, ceramic artists have an ever-expanding palette of colors, effects, and techniques to push their creativity in new directions. https://theartofeducation.edu/2018/05/6-different-ways-to-use-underglazes-with-ceramics/
The Future of Underglazes
As underglazing continues to grow in popularity among ceramic artists, advancements and innovations are expanding the possibilities of the medium. Here are some of the key developments on the horizon for underglazes:
Increased access to a greater variety of colors is allowing for more dynamic and nuanced underglaze work. Brands like Mayco are steadily expanding their underglaze color palettes, while independent makers are also creating custom color mixes.
Underglaze decals and transfers enable ceramic artists to apply intricate, detailed underglaze designs that would be difficult to hand paint. These premade decals provide new decorating options and saves significant time.
Combining underglazes with other techniques like sgraffito, mishima, slip trailing, and more allows for added dimension and visual interest. The layered possibilities are inspiring ceramicists to blend and overlap processes.
3D printing with underglazes is an emerging trend, enabling artists to print underglaze designs and patterns directly onto greenware or bisqueware. As the technology develops, it will unlock unique applications.
Overall, innovations are removing barriers and expanding options for ceramic artists to leverage underglazes’ versatility, precision, and vibrancy in new ways.
