libterm.com Glaze and underglaze are essential techniques in ceramics that enhance both aesthetics and durability of pottery. While glaze creates a smooth, glass-like surface coating that seals and decorates the piece, underglaze offers detailed, vibrant designs painted directly onto the clay before glazing. Explore the differences and applications of these methods to improve your ceramic creations.
Table of Comparison
| Aspect | Glaze | Underglaze | Glaze vs Underglaze |
|---|---|---|---|
| Definition | Glass-like coating fused to pottery surface for shine and protection | Colored decoration applied under a transparent glaze | Glaze is the outer finish; underglaze is the painted design beneath glaze |
| Application | Brushed, dipped, or sprayed onto bisqueware | Painted or stamped on bisqueware before glazing | Glaze covers entire piece; underglaze targets decorative areas |
| Durability | Provides waterproof, protective surface | Durable design sealed by overlying glaze | Underglaze designs are more resistant under glaze |
| Color Quality | May alter colors underneath due to glassy surface | Colors remain vibrant and precise after firing | Underglaze ensures stable color; glaze can affect hue |
| Firing Temperature | Typically fired between 1200-1300degC | Fired at similar temperature but before glaze firing | Both require high heat but applied at different stages |
Understanding Glaze in Ceramics
Understanding glaze in ceramics involves recognizing its function as a glassy coating that enhances both aesthetics and durability by sealing the porous surface of clay bodies. Underglaze refers to colored decoration applied before glazing, allowing intricate designs beneath a transparent or translucent glaze, while glaze itself can be decorative or functional, providing a smooth, waterproof finish. The choice between underglaze and glaze depends on the desired artistic effect and firing technique, impacting color vibrancy and surface texture.
What is Underglaze?
Underglaze is a ceramic decoration technique where colored pigments are applied to pottery before the final clear glaze is added and the piece is fired. Unlike traditional glaze that sits on the surface forming a glassy coating, underglaze colors are embedded beneath the transparent glaze, resulting in durable, vivid designs that resist fading and wear. This method allows artists to create intricate patterns and detailed images, maintaining their clarity after firing at high temperatures.
Key Differences Between Glaze and Underglaze
Glaze is a glassy coating applied over ceramic surfaces to create a smooth, glossy, and waterproof finish, whereas underglaze consists of colored decoration applied directly to the bisque-fired pottery before a clear glaze is added on top. Key differences include the application process, durability, and visual effect; underglaze allows for detailed, matte designs with stable colors that do not run during the final firing, while glaze offers a shiny, protective surface that can alter the appearance of underlying decorations. Underglaze is typically used for intricate patterns and precise artwork, whereas glaze provides the essential functional and aesthetic finish on ceramics.
Composition of Ceramic Glaze
Ceramic glazes consist primarily of silica, alumina, and fluxes, which form a glassy surface when fired, whereas underglazes contain finely ground pigments suspended in a liquid base such as clay slip or water and do not form a glossy coating by themselves. The composition of ceramic glaze includes silica (SiO2) as the glass former, alumina (Al2O3) to provide stability and prevent running, and fluxes like potassium oxide or sodium oxide that lower the melting point. Underglazes, lacking significant silica or flux, are designed to fuse into or bond with the clay body beneath a clear glaze, affecting decoration durability without altering the glaze's glassy surface.
Composition of Underglaze
Underglaze is primarily composed of finely ground pigments suspended in a medium such as clay or flux, allowing it to bond well with ceramic surfaces before the final glaze application. These pigments typically include oxides like cobalt, iron, and copper, which provide vibrant colors that remain stable during firing. In contrast, glaze consists mainly of silica, fluxes, and alumina, forming a glassy surface that seals and protects the painted underglaze beneath.
Application Techniques: Glaze vs. Underglaze
Glaze application involves coating ceramics with a glassy layer that fuses during firing, creating a smooth, often glossy finish that can be applied by dipping, brushing, or spraying. Underglaze is applied directly onto the bisque or greenware clay surface before a clear glaze is applied on top, allowing for detailed designs with precise color control. While glaze application emphasizes surface texture and finish, underglaze focuses on decorative patterns and durability beneath a transparent protective layer.
Firing Process and Its Effects
Underglaze requires a lower firing temperature, typically applied before the final glaze coat, resulting in vibrant, detailed designs that remain stable during high-temperature glaze firing. Glaze firing involves a single high-temperature process, usually between 1200-1300degC, where the glaze melts to form a glass-like surface, enhancing durability and waterproofing. The firing process influences texture and color intensity; underglaze maintains crisp patterns under glaze, while direct glaze firing allows for smooth, glossy finishes.
Color Options: Glaze vs. Underglaze
Glaze offers a wide range of vibrant, glossy colors with a translucent finish that enhances texture and depth on ceramic surfaces. Underglaze provides precise, matte or satin colors that remain stable during firing, ideal for detailed designs and layering without bleeding. Choosing between glaze and underglaze depends on desired color intensity, finish, and complexity of ceramic artwork.
When to Use Glaze or Underglaze
Use glaze when you want a glossy, protective finish that enhances color depth and durability on ceramics, ideal for functional pottery and finished surfaces. Underglaze is best suited for detailed designs and intricate artwork applied before the final glaze, providing precise color control and sharp patterns beneath a clear or translucent coating. Choose glaze for surface protection and richness, while underglaze is optimal for fine decoration requiring stable, vivid colors under a smooth glaze layer.
Pros and Cons of Glaze and Underglaze
Glaze offers a glossy, durable finish that enhances color vibrancy and provides a protective barrier against moisture and wear, making it ideal for functional pottery; however, it can sometimes obscure fine details and requires careful application to avoid defects like crazing or blistering. Underglaze allows precise, detailed decoration with vibrant colors that remain stable under the glaze, offering greater control for intricate designs, but it lacks the protective qualities of a full glaze layer and may require a clear glaze overlay to ensure durability. Choosing between glaze and underglaze depends on the desired aesthetic, functional needs, and firing process compatibility in ceramic projects.
Glaze, Underglaze Infographic
