Ceramics Glossary
Find definitions for ceramic terms, materials, techniques, and tools.
Discover glossary terms
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.
KintsugiKintsugi is a Japanese ceramic repair technique that consists of joining the broken parts of a piece using a resin-based adhesive mixed with gold, silver or platinum powder. This practice not only restores the functionality of the piece, but also highlights cracks and breaks as decorative elements, transforming imperfections into integral parts of the object's history and beauty. Kintsugi is based on the philosophy of wabi-sabi, which values imperfection and transience, symbolizing resilience and continuity.
In addition to its aesthetic and philosophical significance, kintsugi also promotes a mindset of accepting and valuing imperfection, teaching that breakages and repairs can add unique and personal value to pieces. This technique has gained worldwide recognition as an art form that combines functionality with beauty and deepens the emotional connection to the object.
Jigger and jollyJiggering and jollying are mechanical forming techniques used in ceramics to produce uniform, symmetrical objects such as plates, bowls, and cups. In these processes, a lump of clay is placed onto a rotating plaster mold. A shaped template or arm (often referred to as a “profile tool”) is then introduced, which sculpts the clay against the mold. Jiggering typically refers to the operation where the outside of a piece is formed by the profile tool while the plaster mold defines the inside shape, whereas jollying is essentially the inverse, with the plaster mold setting the external shape and the profile tool sculpting the interior. These techniques allow for rapid, repeatable production of ceramic ware with consistent thicknesses and dimensions, particularly useful in industrial or semi-industrial settings where large batches of identical pieces are required.
Stack and slam kneadingStack and slam kneading involves cutting the clay into sections with a string or cutting wire, stacking the sections on top of each other, and then pounding or pressing them together repeatedly. This process is repeated several times until the clay has a uniform consistency and no entrapped air.
Stack and slam is especially useful when working with large quantities of clay, as it is less physically demanding than other techniques such as spiral kneading.
In industrial production ceramics studios or in workshops that create large pieces, Stack and slam kneading is a standard technique; it is also useful when recycling clay that has been reused from previous work.
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.
Thermal expansionThermal expansion refers to the expansion that clays, clay bodys and glazes undergo when exposed to heat in the kiln. This phenomenon occurs because the increase in temperature causes increased vibration of the molecules, causing the materials to expand. During firing, this expansion is gradual, but in the cooling stage, the materials begin to contract. The correct understanding of thermal expansion is fundamental to avoid structural defects in ceramic pieces.
If the coefficient of thermal expansion of the glaze does not match that of the clay body, internal stresses occur in the part. These stresses can cause common problems such as cracking, spalling, or fracture. To avoid these problems, glazes and clays with compatible coefficients of expansion must be formulated. Proper choice of materials is especially critical in utility ceramics, where exposure to sudden temperature changes can cause thermal shocks that damage the part.
LepidoliteLepidolite is a lithium-rich mineral that is used in ceramics primarily as a flux, playing a crucial role in lowering the melting point of glazes, allowing them to vitrify at lower temperatures. Lepidolite is especially useful in the manufacture of low-temperature ceramics, such as earthenware, where complete vitrification is required without the need for extremely high temperatures.
In addition to its properties as a flux, lepidolite has the ability to modify glaze colors, producing clayl shades. Colors derived from lepidolite can include shades such as pinks, lilacs, pale greens or soft blues, which are difficult to obtain with other fluxes without the need to subject the pieces to high temperatures. In particular, lepidolite is used to obtain translucent glazes that provide a soft and luminous finish to ceramic pieces.
Bow CutterThe bow cutter, is a tool used to cut blocks of clay or divide modeled pieces in a precise manner. It consists of an arched frame that holds a taut wire, allowing uniform and clean cuts to be made. It is especially useful in production workshops where it is necessary to work with large volumes of clay or in techniques such as neriage, where it is necessary to cut and recombine layers of clay of different colors.
The design of the bow cutter makes it easy to cut large or complex pieces without deforming them, making it an essential tool for potters working with slabs or blocks of clay. It is also used in decorative techniques, such as cutting sections of clay to expose internal patterns.
Pycnometer or densimeterThe pycnometer or densimeter is a tool used to measure the density of liquids such as slips, glazes and engobes. This measurement is crucial to ensure that these materials have the right consistency for their application. Correct density ensures that the slip flows evenly during casting in molds and that the glazes adhere properly to the pieces without running off or forming uneven layers.
The pycnometer measures density by comparing the mass of a known volume of liquid to the mass of the same volume of water. This process allows the proportions of water, clay and other components to be adjusted to obtain consistent results. Density meters are especially useful in industrial production and in workshops working with precise formulas.
AshAsh is the mineral residue left after the combustion of organic materials, such as wood or bones. These ash particles can be incorporated into clays, glazes or during modeling. Ash can add unique textures, colors and physical properties to pieces, depending on its chemical composition and the way it is integrated into the clay or glaze.
In addition, ash can act as a flux, helping to reduce the melting temperature of materials in the glaze and promoting more uniform vitrification during firing. This can improve the durability and water resistance of ceramic pieces, as well as add a gloss or matte finish depending on the technique used. The inclusion of ash can also influence the texture and final appearance of the piece, providing interesting visual effects that complement the overall design.
