Ceramics Glossary
Find definitions for ceramic terms, materials, techniques, and tools.
Discover glossary terms
Bismuth subnitrate (BiONO₃)Bismuth subnitrate is a chemical compound used in ceramics to create opaque, pale yellow and soft white glazes. Bismuth, the main heavy metal in this compound, is noted for being non-toxic, making it a safer alternative to other heavy metal compounds, such as lead. Thanks to its non-toxic properties, bismuth subnitrate has gained popularity as a component in ceramic glazes for tableware and other household products, allowing the creation of pieces without the risks associated with the use of lead.
In addition, bismuth subnitrate is increasingly used in contemporary ceramics due to its opacifying properties and its ability to generate finishes with a smooth and elegant texture. This makes it ideal not only in the production of tableware and household utensils, but also in artistic pieces and luxury ceramics, where the aesthetics of the finishes and the safety of the final product are essential aspects.
FinishingFinishing refers to the techniques and processes applied to a piece once it has been shaped and fired to enhance its aesthetic appearance and functionality. This process can include a variety of methods, such as glazing, painting, engraving, glazing and the application of textures. The finish is crucial in defining the final appearance of the ceramic piece, as it determines its color, gloss, texture and resistance to external factors such as wear and liquid absorption.
There are different types of finishes that can be applied depending on the style and purpose of the piece. For example, a gloss finish can provide a polished and professional appearance, while a matte finish can offer a more rustic and natural aesthetic. In addition, finishes can include additional decorative elements, such as reliefs, engravings or inlaid materials, which add depth and detail to ceramic pieces.
MochaCeramic mocha is a traditional decorative technique that relies on the physical and chemical properties of ceramic suspensions and alkaline solutions to create dendritic, organic and random patterns on the surface of the piece.
The process begins with the application of a fresh engobe (a mixture of clay and water) on the surface of the raw or partially dried piece. While the engobe maintains a high moisture content, an alkaline solution mixed with a pigment (e.g., metal oxides or ceramic colorants) is carefully added. Upon contact with the wet engobe, the alkaline solution generates a different surface tension and promotes the "migration" of the pigment, which branches by capillarity, producing patterns reminiscent of agate veins.
The particularity of the mocha lies in the spontaneity and unpredictability of its patterns: each application generates a unique and unrepeatable design, difficult to control completely, which gives the piece a marked artisanal and aesthetic value. The variety of results obtained with mocha depends on numerous factors: the composition of the engobe, the concentration of the alkali, the fluidity of the pigment, the ambient humidity, the method of application and even the inclination or movement of the piece.
MuffleThe muffle is an internal, refractory chamber installed inside a kiln, designed to isolate the pieces from direct contact with the flames, combustion gases and ashes generated by the fuels. This lining forms a protected zone in which the pieces are fired under controlled conditions, which is essential when looking for specific effects or very precise atmospheres during firing. Unlike direct fire firing, the use of a muffle makes it possible to maintain a more stable internal atmosphere, minimize the presence of impurities and better control the final quality of glazes, polishes and sensitive surfaces.
This technique has its origins in ancient ceramic traditions, such as Islamic and Chinese, in which internal chambers were used to fire delicate porcelains and demanding glazes. In this way, muffles ensured chromatic purity and surface uniformity, preventing unwanted substances from altering the final appearance of the pieces. Today, muffles are especially valuable in kilns fired with gas, wood or coal, where smoke, ash and sudden changes in atmosphere could drastically alter the results.
TemplateThe template is an essential tool in ceramic work, designed to facilitate the creation of consistent and precise shapes. Usually made from materials such as cardboard, wood, plastic or metal, the template serves as a guide for trimming or shaping clay into specific forms during techniques such as plate modeling, hand building or even the pottery wheel. It is also used to ensure that the components of a part, such as the walls of a vase or the panels of a box, have uniform dimensions.
Templates are not only functional in the structural construction of parts, but are also valuable in decoration. In techniques such as stenciling, templates allow repetitive designs to be applied with precision, using engobes, glazes or even textures. In addition, custom stencils provide the freedom to explore unique shapes and patterns that can become a hallmark of your work.
In mass production, templates are especially useful for ensuring uniformity between parts, reducing errors and optimizing working time. They are a versatile tool, as they can be easily adapted to specific projects by simply adjusting their size or shape.
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.
Semi-matte or satinatedSemi-matte or satinated refers to a type of ceramic glaze that has an intermediate finish between gloss and matte. This type of glaze offers a soft satin sheen that is neither completely opaque nor fully reflective, providing an elegant, restrained appearance to ceramic pieces. Semi-matte glazes achieve this balance by incorporating specific components that subtly scatter light.
In addition, semi-matte glazes facilitate the creation of smooth, gradual transitions between different colors and tones, allowing for more complex and harmonious designs. Their ability to hide small imperfections in the clay also contributes to a more uniform and refined finish. The application of semi-matte glazes requires careful balance in formulation and precise firing control to achieve the desired level of gloss and opacity.
Tincar ClayTincar clay is a special clay used mainly in handmade ceramics and sculpture. It is known for its smooth texture and its ability to hold fine details during the modeling process. Tincar is especially prized for its light color and ease of workability, making it ideal for pieces that require a smooth, soft surface. This clay is used both for hand modeling and for use in molds, and is known for its good moisture retention capacity, which allows for greater flexibility during the modeling phase.
The name "Tíncar" is specific to some types of clays that can be found in various regions, and their exact composition can vary according to the place of extraction. In general, Tíncar clays are composed mainly of kaolin and silicates, which makes them more suitable for firing at low temperatures and for achieving white and fine finishes.
UnderglazeThe "underglaze" decoration technique consists of applying colors or pigments to a piece before it is covered with a glaze. Underglaze colors are applied to the piece in a raw or bisque state, that is, before the final glaze has been applied or before the piece is fired. This technique is widely used in decorative ceramics, as it allows the colors to fuse with the glaze during the firing process, which not only protects them, but also gives them a glossy and durable finish. Unlike glazes applied over a fired ceramic layer, underglaze colors are more deeply integrated with the piece, creating a more uniform appearance with a vitreous appearance after firing.
In some cases, pigments are mixed with a gum, such as arabic gum, to help fix the colors to the ceramic surface prior to glaze application. This fixative ensures that the pigments do not slip or mix with the glaze when applied, thus maintaining the definition and precision of the design.
The underglaze technique also allows the creation of detailed and complex designs, as the pigments can be applied with precision before the final firing. One of the most famous applications of the underglaze technique is seen in traditional Delft pottery. In this technique, blue-on-white patterns are applied using blue pigments under a layer of transparent glaze, creating the distinctive style of Delft pottery.
FritFrit is an intermediate product in the manufacture of ceramic glazes, essential to control and improve the final properties of the glazed piece. It is obtained by melting a carefully formulated mixture of oxides (such as silica, metal oxides, borates, aluminates) at very high temperatures, usually in a kiln specifically designed for its production. Once molten, the resulting vitreous mass is rapidly cooled (e.g., by pouring it into cold water) to obtain a brittle glass, known as "raw frit". This glass is then ground to a fine, homogeneous powder. Frit production is a highly specialized branch of the ceramic industry, with laboratories dedicated to formulating compositions to achieve innovative effects and improve the technical properties of glazes.
Frit serves several purposes: first, it helps stabilize reactive compounds, reducing the volatility and toxicity of certain components, such as lead or barium, by incorporating them into the glassy network. This makes glaze handling safer and the finished piece complies with food safety standards. In addition, frits allow precise control of the chemical composition of the glaze, which translates into greater predictability and reproducibility of firing results. As a result, glazes can be created with very specific colors, gloss, textures and degrees of transparency, adapted to different climates, kiln atmospheres and firing temperatures.
