Ceramics Glossary
Find definitions for ceramic terms, materials, techniques, and tools.
Discover glossary terms
Color stabilityColor stability refers to the ability of the colors and glazes used in a piece to maintain their original appearance under various environmental conditions and over time. This property is crucial to ensure that ceramic works retain their color and brightness, avoiding fading, changes in tone or discolorations that may affect their aesthetics and value.
Color stability depends on several factors, including the chemical composition of the glazes, application techniques and firing conditions. It is important to select high quality glazes that offer resistance to light, heat and moisture to ensure that colors remain vibrant and consistent over time.
In addition, the correct preparation and application of glazes contributes significantly to their stability, avoiding defects such as bubbling, cracking or peeling that can compromise color integrity.
UlexiteUlexite, also known as "television stone", is a borate-rich mineral used mainly in ceramics as a flux in glazes. Its main function is to lower the melting point of glazes, which allows glossy, well vitrified finishes to be obtained without the need for firing at excessively high temperatures. Ulexite also improves the adhesion of the glazes to the pieces and gives them greater durability.
In addition to being an excellent flux, ulexite can contribute to the creation of unique visual effects on the glaze surface, creating interesting patterns or smooth textures, depending on kiln conditions and the concentration of ulexite in the mixture.
Kiln furnitureKiln furniture are refractory elements, usually shelves or disks, which are placed between the ceramic pieces stacked in the kiln during firing. Their main function is to prevent the pieces from touching and sticking together as the glazes melt, ensuring that each object maintains its individual shape and finish. This furniture allow the hot air to circulate evenly around the pieces, promoting a homogeneous firing and preventing deformations or defects caused by direct contact between the pieces.
There are different types of kiln furniture depending on the type of kiln and the specific firing requirements. Some are made of insulating materials that help maintain a constant temperature at each kiln level, while others can be of various shapes and sizes to adapt to different types and sizes of parts.
In addition to preventing sticking, kiln furniture contributes to kiln energy efficiency by improving heat circulation and reducing thermal losses. Their correct use can extend the service life of kiln shelves, preventing them from being damaged by direct contact with hot glazeed parts.
Glazing techniquesGlazing techniques are the methods by which glaze is applied to ceramic pieces.
There are different approaches to achieve different visual and textural effects, depending on the type of glaze and the style of the piece. Each technique has its own particularities in terms of coverage, amount of glaze and the control it offers.
<u>Dipping</u>
Dipping is a fast and efficient application technique, especially suited to cover small to medium-sized pieces evenly. They are completely immersed in an glaze bath, allowed to drain and then dried before firing. This technique is especially useful when even coverage is desired and large quantities of parts are to be glazeed.
<b>Helpful Tip:</b> Control the dipping time and viscosity of the glaze to prevent the coating from being too thick and causing run-off or flaws.
<u>Spraying</u>
The use of airbrushes or sprayers to apply glaze offers greater control and allows you to work on large pieces or with irregular surfaces. It is ideal for obtaining gradient effects or applying glaze in thin layers. This technique requires specialized equipment and often a ventilated work space.
<b>Helpful Tip:</b> Test on test pieces to adjust the amount of air and distance when spraying, which will allow you to achieve a perfect finish without accumulating too much glaze in one area.
<u>Pouring</u>
Pouring glaze consists of pouring the glaze directly onto the piece, allowing it to flow over the surface. This method is useful for larger pieces and can generate interesting effects, such as natural lines or patterns, depending on how the glaze is poured.
<b>Helpful Tip:</b> Make sure the excess glaze drains completely before firing to avoid buildup on the base that could cause the piece to stick to the kiln shelf.
<u>Brushing</u>
The technique of glaze brushing uses brushes, sponges or similar tools to apply glaze in a precise and detailed manner. It is ideal for adding patterns, fine details and elaborate decorations. This method requires patience and control, as the glaze may not behave like traditional paint.
<b>Helpful Tip:</b> Use soft bristle brushes for precision and thin the glaze if necessary to achieve fine, even lines.
Chromium oxide (Cr₂O₂O₃)Chromium oxide is a versatile ceramic pigment, widely used to create deep and vibrant green tones in glazes and engobes. Its chemical stability allows it to retain color even in high temperature firings, making it a reliable and durable colorant.
In addition to intense greens, chromium oxide can produce pink or reddish hues when combined with other components and under specific firing atmospheres, extending its decorative range.
In traditional ceramics, such as Islamic earthenware, it is appreciated for its bright and permanent green tones, which have been part of its distinctive aesthetics over the centuries.
VolatilizationThe term volatilizing refers to the process by which certain materials, such as metal oxides, evaporate at high temperatures and are then redeposited in other areas of the kiln or on other ceramic pieces during firing. This phenomenon is common in high-temperature firings, where chemical compounds present in glazes or clay can sublimate and move as vapor within the kiln environment.
Volatilization can have both positive and negative effects on the finish of ceramic pieces. On the one hand, it can be used intentionally to create unique decorative effects, such as colored spots, irregular textures or gradients in the glaze. On the other hand, uncontrolled volatilization can cause unwanted defects, such as discolorations, irregular stains or loss of fine details in the applied decorations.
Volatilization management is crucial to maintain the quality and consistency of ceramic pieces, especially in industrial production processes where repeatability and precision are critical. This involves carefully selecting vitrifying materials, adjusting firing conditions and using appropriate ventilation or filtration systems to control the spread of vapors within the kiln.
OxidesOxides are chemical compounds formed by the combination of oxygen with metallic elements. In ceramics, oxides play an essential role in creating a wide range of colors in glazes and engobes. Each type of oxide produces a distinctive color when fired at high temperatures in the kiln, and the final result can be influenced by the firing atmosphere, whether oxidizing or reducing. The most common oxides used in ceramics include cobalt oxide, which generates intense blue tones; copper oxide, responsible for deep greens and sometimes metallic colors; and iron oxide, which contributes reds, browns and blacks depending on firing conditions. Other oxides, such as manganese oxide, nickel oxide and titanium oxide, are also used to expand the palette of available colors, allowing experimentation with a wide range of shades and decorative effects.
The interaction of these oxides with the clay and other glaze components is crucial in determining the final color and texture of the ceramic piece. For example, cobalt oxide not only provides a deep blue, but can also influence the translucency and luster of the glaze. Copper oxide, depending on the amount used and the firing atmosphere, can produce everything from bright greens to darker, earthier tones.
In addition to their decorative function, oxides can also influence the physical properties of the glaze, such as its resistance to wear, its impermeability and its adhesion to the clay surface. The correct selection and mixture of oxides is essential to achieve the desired balance between aesthetics and functionality in ceramic pieces.
Needle toolThe awl is a ceramic tool with a fine, sharp point, designed for precise incisions and decorative details on the surface of clay pieces. Made from materials such as metal, wood or plastic, the needle tool is used for techniques such as sgraffito, where a surface layer of engobe or glaze is scraped away to reveal the underlying color or texture. It is also commonly employed to mark patterns, fine lines or functional perforations on pieces.
The design of the needle tool varies according to its purpose. Some have straight, thin tips, ideal for sharp lines, while others have slightly curved or needle-like ends to create more varied decorative effects. In utilitarian ceramics, the needle tool can also be used to punch small holes in pieces such as incense burners or cooking utensils.
AirbrushAn airbrush is a tool that is connected to an air compressor and is used to apply glazes, engobes or any other type of coating on the surface of ceramic pieces. Through controlled spraying, the airbrush allows a smooth and uniform application of the material, which facilitates obtaining fine and detailed finishes.
This technique is especially useful for creating visual effects such as color gradients, soft shading or thin layers of glaze that do not build up excessively. In addition, it is ideal for both large-scale work, such as sculptures, and precision work, allowing delicate details without the need for multiple layers.
Copper carbonate (CuCO₃)Copper carbonate is one of the most versatile colorants in ceramics, known to produce a wide range of colors (greens, blues, reds and browns) in glazes and engobes. The resulting shade depends largely on the firing conditions: in an oxidizing atmosphere, copper carbonate usually produces a bright green, while in a reducing atmosphere it can be transformed into red or brown tones. At medium and high firing temperatures, its performance becomes more stable, allowing intense and vibrant colors that are popular in stoneware and porcelain.
In addition, copper carbonate can be used in layered glaze techniques or in combination with other oxides to create textured and varied effects, from stains to color gradations. It is also common in cuerda seca and majolica decorations, where it adds distinctive color to geometric and floral designs.
