Ceramics Glossary
Find definitions for ceramic terms, materials, techniques, and tools.
Discover glossary terms
ThixotropyThixotropy is a physical property of ceramic suspensions, such as slip, that describes how they become more liquid when agitated, mixed or subjected to mechanical forces, but regain their thick consistency when at rest. This property is especially important in slip casting, where the slip must flow easily to coat the inner surfaces of the molds but must remain thick enough to form a solid, uniform layer once poured. In addition, in the application of engobes and glazes, thixotropy ensures that coatings are evenly distributed without drips or unwanted buildup.
In practice, thixotropy is achieved by the addition of deflocculants or thickeners that adjust the viscosity of the material according to the working conditions. When the slip is subjected to agitation, external forces break the internal interactions between the particles, reducing the viscosity and allowing the liquid to flow freely. When agitation is stopped, these interactions are quickly restored, returning the slip to a thicker, more stable state that prevents particle settling and maintains an even distribution of the applied material.
Crenellation or battlementCrenellation is a decorative design characterized by a series of regular geometric shapes, such as rectangles or squares, arranged alternately to create a rhythmic and dynamic visual pattern. Inspired by the battlements of medieval fortifications, this motif is widely used in both functional and decorative ceramics. It is applied in borders, friezes, tiles, plates and vases, providing an architectural and ornamental touch that evokes strength and protection.
In ceramics, the crenellated design can be created by various techniques, such as sgraffito, where the surface of the clay is scraped to reveal underlying layers, or by the application of contrasting engobes and glazes to highlight the design. Precision in the execution of crenellation is key to achieving a balanced and attractive effect, especially on pieces that require repetitive patterns.
Historically, the crenellated motif has been widely used in Islamic ceramics, where it was combined with intricate geometric patterns to decorate palaces, mosques and utilitarian objects. Its symbolism associated with strength and protection makes it a popular choice in contemporary architectural and ceramic pieces.
GlassGlass in ceramics refers both to the vitreous component that forms in ceramic glazes and to the direct use of glass fragments or powder to decorate the surface of the pieces. In glazes, glass is formed by melting during firing, creating a hard, shiny and resistant layer that not only beautifies the piece, but also waterproofs it and protects it against physical and chemical damage. This vitreous coating provides a uniform and aesthetically appealing finish. In addition to use in glazes, glass shards or crushed glass powder can be applied directly to the clay prior to firing for unique visual effects, such as glossy, speckled or textured surfaces, which add an extra dimension to the ceramic piece.
Glass in ceramics not only serves an aesthetic function, but also enhances the functional properties of the pieces. By acting as a vitrifying agent, glass increases the water resistance and durability of the pieces, making them more suitable for utilitarian applications such as tableware, vases and cookware.
Third fireThird fire, is a ceramic technique that involves applying a new layer of decoration or glaze on a previously glazed and fired piece. Subsequently, the piece undergoes an additional firing at lower temperatures, usually between 750 °C and 800 °C, which ensures that the new decoration adheres without altering the base glaze or the integrity of the piece.
This technique is especially used to add fine decorative details, such as metallic luster, ceramic decals, or overglaze effects. Thanks to the low firing temperature, the applied colors, metals and decorations maintain their brilliance and definition without the risk of burning or fading, making it ideal for achieving complex and sophisticated finishes.
Third fire is a versatile and highly precise technique, which requires care in application and temperature control to avoid defects such as bubbles or flaking. It is widely used in both handmade ceramics and industrial production, where it is used to create pieces with high quality finishes.
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Slip castingSlip casting is a versatile ceramic forming method that takes advantage of gypsum's ability to absorb water. The process begins with the preparation of a slurry, a fluid mixture of fine clay and water, often with deflocculants to reduce viscosity. This slip is poured into a plaster mold, whose porous walls draw the water out, progressively solidifying a layer of clay against its inner surface. When the desired thickness is reached, the excess slip is removed, leaving a hollow "shell" of clay in the exact shape of the mold.
Once the piece has reached the proper consistency, it is removed from the mold to dry completely before firing. This process is particularly suitable for the mass production of complex, light and uniform shapes, such as tableware, decorative figures and technical components.
Screen printing screen or silk screenA silk screen is a tool composed of a frame on which a fine mesh, traditionally made of silk or nowadays of nylon or polyester, is stretched. This mesh contains areas that are permeable and impermeable to the passage of ink or ceramic engobe. By pressing the coloring medium with a squeegee through the mesh, the design is transferred to the surface of the piece, whether it is a tile, plate, cup or any other ceramic object.
Screen printing makes it possible to reproduce complex designs, repetitive patterns or even detailed illustrations with high precision. This is especially useful in the industrial or semi-craft production of tableware, tiles and decorative pieces, as it ensures uniformity, consistency and speed in decoration.
Potassium dichromate (K₂Cr₂O₇).Potassium dichromate is a chemical compound that has historically been used in ceramics to produce vibrant colors, especially bright shades of orange and yellow, in glazes and engobes. This compound is known for its ability to react at high temperatures, resulting in intense, highly saturated colors.
Potassium dichromate is particularly valuable in ceramic glazes where a wide range of warm shades are sought, from golden yellows to intense oranges, which are difficult to obtain with other compounds. Its reactivity at high temperatures allows the color to be more stable during the firing process, which facilitates control and predictability of the results.
However, the use of potassium dichromate has decreased significantly in modern ceramics due to its toxicity. The compound contains hexavalent chromium, which is a highly toxic and carcinogenic agent. This has led to increased awareness of its handling and has prompted the search for safer alternatives, especially in food-grade ceramics and in parts that come into contact with the skin.
Banding wheelThe banding wheel is an essential tool in ceramics, designed to facilitate decorative and finishing work on pieces. Unlike the pottery wheel, which is generally larger and motorized, the banding wheel is a small, hand-operated turntable that allows the piece to be rotated with precision and control. This slow and steady turning capability is essential for applying fine details, adjusting decorations and performing delicate touch-ups without the need to physically move the part.
The banding wheel is used at various stages of the ceramic process, including applying glazes, drawing decorative patterns, creating reliefs and setting structural details. Its compact and portable design allows the user to work comfortably and maintain an ergonomic posture for long periods of time, thus improving the efficiency and quality of the work performed.
Sodium PolyacrylateSodium polyacrylate is a synthetic polymer that plays a role mainly as a dispersant in slip, engobes and glazes. Its main function is to improve the flowability of ceramic mixtures by reducing viscosity without adding more water. This allows working with less water content, which in turn reduces shrinkage and the risk of deformation or cracking during drying and firing.
In slip, sodium polyacrylate ensures that clay particles and other materials remain in suspension, preventing sedimentation and guaranteeing a homogeneous mixture. This is especially important in techniques such as casting, where an even distribution of materials is essential to obtain well-formed parts. In addition, this polymer is useful in glazes and engobes, where it facilitates smooth and consistent application.
Despite its functionality, the use of sodium polyacrylate requires caution, since an excessive amount can cause over-dispersion, hindering the cohesion of the materials. Therefore, it is essential to adjust the proportions carefully and to test beforehand.
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.
