Ceramics Glossary
Find definitions for ceramic terms, materials, techniques, and tools.
Discover glossary terms
Bas-reliefBas-relief is a sculpting technique applied to ceramics that consists of creating slightly protruding decorations on the surface of the piece, in contrast to high relief where the elements protrude significantly. In bas-relief, the figures or patterns have a moderate depth that gives them a subtle but visible appearance, allowing the details to be appreciated from different angles. This technique is commonly used to add decorative embellishments, elaborate borders and geometric patterns, enriching the aesthetics of the piece without compromising its structural integrity.
Bas-relief allows the incorporation of decorative elements that add texture and complexity to the pieces, creating a balance between flat form and three-dimensional shapes. This technique can be used to depict a variety of subjects, from natural motifs such as flowers and leaves to abstract and geometric patterns. In addition, bas-relief can be combined with other decorative techniques, such as glazing and engobe painting, to achieve more elaborate and personalized finishes.
Raku tongsRaku tongs are metal tools designed to handle hot ceramic pieces during the raku firing process. These tongs, usually long and sturdy, allow the pieces to be removed from the kiln while they are still red-hot and safely transported to containers with combustible materials, such as sawdust or paper, where the characteristic raku effects, such as crackle and smoky finishes, are generated.
The design of the tongs is intended to provide a firm grip without damaging the surface of the pieces, which is crucial in a process where ceramics are extremely fragile due to the high temperatures.
Vanadium pentaoxide (V₂O5)Vanadium pentaoxide (V₂O₅) is a refined and highly reactive form of vanadium that is used in ceramics to create intense and vibrant colors, especially in yellow and sometimes green and brown shades when combined with other elements. This compound is known to provide a luminosity and depth of color that shines through in both opaque and semi-transparent glazes.
Its ability to integrate well into glaze mixtures makes it an excellent complement to oxide combinations, such as chrome or iron, creating complex and dynamic effects on ceramic surfaces. When applied in different types of clays and under various firing atmospheres, this oxide allows obtaining from warm, sunny yellows to deeper, earthy tones, which makes it extremely versatile in decorative projects.
.jpg/small)
Glossy (Glaze)The glossy surface in ceramics refers to a highly reflective and smooth to the touch glaze finish, which gives the pieces a polished appearance. This type of finish is valued in both utilitarian and decorative pieces, as it not only enhances visual aesthetics but also facilitates cleaning and hygiene maintenance. Glossy glazes enhance the colors and details of the piece, offering a vibrant and attractive appearance that highlights the quality and care in its manufacture.
To achieve a glossy surface, the glaze should be applied evenly in thin layers and then fired at the proper temperature to fully vitrify. The correct formulation of the glaze, which includes a balanced mixture of silica, alumina and fluxes, is essential to obtain a glossy finish without defects such as bubbles, cracks or flaking.
Cristobalite (SiO₂)Cristobalite is a form of silica (silicon dioxide) characterized by its unique crystalline structure, which makes it particularly resistant to extremely high temperatures. It forms naturally in volcanic environments and, due to its ability to withstand thermal changes, is highly valued in ceramics.
Cristobalite is mainly used to improve the thermal stability of clay bodys and glazes, helping to prevent cracking or deformation of the pieces when exposed to extreme thermal cycles. Its incorporation in clay bodys also helps reduce shrinkage during firing, making it an ideal additive for clays that tend to warp or crack as they dry or fire.
In addition to its heat-resistant properties, it also improves durability and the ability of parts to withstand demanding conditions of use, making it a key component in the production of technical and refractory ceramics.
Cobalt Oxide (Co₃O₄)Cobalt oxide (Co₃O₄) is one of the most widely used pigments in ceramics, known for its ability to generate a wide range of blue hues. This oxide is highly potent, meaning that even small amounts can produce intense and deep colors. Its chemical and thermal stability makes it an ideal choice for use in glazes and engobes over the entire temperature range, from low to high firing.
In transparent glazes, cobalt oxide produces a vivid, uniform blue, while in opaque or textured glazes it can generate complex visual effects, such as speckled patterns or color gradients. In combination with other oxides, it can produce secondary colors, such as bluish greens when mixed with copper oxide or deep purples when combined with manganese.
TalcTalc is a magnesium silicate mineral used in ceramics mainly as a degreaser and to modify the texture and melting of ceramic glazes. Its main advantage lies in its ability to improve the plasticity of the clay, making the clay body more malleable and flexible, which facilitates the formation and modeling of pieces. In addition, talc also contributes to the thermal stability of the pieces during firing, helping the pieces not to deform or crack under extreme temperatures.
It is particularly useful when working with clays that need improved workability or when seeking to avoid excessive shrinkage during drying and firing.
Zinc oxide (ZnO)Zinc oxide is a versatile compound in ceramics, mainly used to adjust the texture of glazes and to achieve matte and satin finishes. This material is especially useful in the formulation of satin or semi-matt glazes, providing visual smoothness and a surface that is pleasant to the touch. In addition, zinc oxide acts as a stabilizer in glazes, helping to reduce the risk of cracking, a valuable quality for the durability of utilitarian and decorative pieces.
This oxide can also influence the final colors of glazes when combined with other colorants, achieving opacity effects or even crystalline effects under certain firing conditions. In high-temperature glazes, zinc oxide contributes to improve the stability and resistance of the finish, allowing glazes to maintain their appearance and texture even under conditions of intense use.
Ball clayBall clay is a type of highly plastic, pale-colored clay, recognized for its excellent modeling ability and high strength once fired. This clay is a mixture of finely ground minerals, mainly kaolin, and often contains additives such as bentonite to improve its plasticity. Ball clay is one of the most common ingredients in the manufacture of pottery wheel clays due to its malleability and ease of handling, making it ideal for the creation of utilitarian pieces such as cups, plates and vases that require precise shapes and fine details.
Due to its high plasticity, ball clay allows for detailed handling and effective adhesion between the different parts of a ceramic piece. However, its softness also makes it more susceptible to deformation and cracking during drying and firing, so it is often mixed with other types of clay or degreasers such as grog to improve its stability and reduce shrinkage. This clay is fired at high temperatures, which gives it great strength and durability, making it suitable for both utilitarian and decorative ceramics.
FluxFlux is an essential substance in the chemistry of clay bodys and glazes, as it has the power to lower the temperature at which silica particles and other components begin to melt. By acting as a glassy phase facilitator, flux helps ceramics reach vitrification, a state in which the clay becomes dense, nonporous and tough, and the glaze surface is transformed into a glossy or matte glassy coating, depending on the formulation.
Fluxes can be of natural origin (such as feldspars, dolomite, limestone, vegetable ashes or nepheline syenite) or synthetically produced. Their choice and proportion in the mixture are decisive for the final properties of the piece. For example, the presence of certain fluxes influences the gloss, transparency, opacity, color and chemical resistance of the glaze. In clay bodys, a suitable flux allows the piece to be fired at lower temperatures, reducing energy costs and expanding the range of materials that can be worked.
Historically, the discovery and use of fluxes mark milestones in ceramics. From vegetable ashes in ancient China, which gave rise to porcelain, to the use of feldspars in Europe, fluxes have made it possible to develop new aesthetics, improve the quality of the final product and diversify ceramic techniques.
