Glaze & underglaze is used in ceramic arts to add color & texture. Glaze is a thin layer of liquid clay applied to the surface & then fired to form a hard, glossy coating. Underglaze is applied directly to the raw clay before glazing & is protected by the glaze layer. Underglaze provides a long-lasting color, while glaze is used to create effects, such as a crackled or textured surface.
| Feature/Aspect | Glaze | Underglaze |
|---|---|---|
| Application Layer | Outermost after firing | Direct on raw clay |
| Translucency | Varies | Generally opaque |
| Finish Options | Glossy, matte, etc. | Mostly matte |
| Purpose | Protection, aesthetics | Decoration |
| Application Stage | After bisque firing | Before any firing |
| Longevity of Color | Varies | Stable |
| Texture Effects | Varies | Show clay texture |
| Protection | Yes | Requires glaze cover |
The Differences Between Glaze and Underglaze
In ceramic arts, glaze and underglaze are two separate substances used to color and finish the surface of clay objects. Applied to the surface of the item and fired to form a hard, protective covering, glaze is a thin, translucent or opaque coating consisting of melted glass or ceramic material.
Glaze
When applied to the surface of pottery, ceramics, or other comparable things, glaze is a thin layer of molten glass or ceramic substance. It is employed to improve the object’s usefulness, durability, and aesthetic appeal.
One of glaze’s main advantages is its capacity to give ceramics a shiny, smooth finish. This results in a stunning, lustrous finish that is impervious to stains, dampness, and general wear and tear.
The glaze’s capacity to protect the pottery is another advantage. The object is made more enduring and damage-resistant with the help of glaze, which also makes cleaning it simpler. Additionally, it aids in preventing liquid absorption, which can result in the pottery becoming stained or discolored.
Glass and ceramics can both be used to make glaze, which can then be formed to produce a variety of colors and finishes. While some glazes are opaque, others are translucent. Some glazes have a glossy sheen, while others are matte.
Underglaze
Underglaze is a coloring agent that is applied directly to the unglazed clay before glazing. Underglaze color is stable and shielded by the glaze layer, unlike glaze, which can shatter or change appearance with time. The major distinction between a glaze and an underglaze is that a glaze creates a protective layer, whereas an underglaze gives a ceramic item a consistent hue.
Before glazing, underglaze is a substance used in ceramics to provide color to the unglazed clay surface. Underglaze comes in a variety of forms, each having special qualities and applications.
Types Of Underglaze
Opaque Underglazes
These underglazes offer a solid, strong color that totally covers the clay surface. Opaque underglazes are a form of underglaze used in ceramics to give the surface of unfired clay a solid, strong hue. Their capacity to totally cover the clay and hide the underlying surface distinguishes them. In order to permanently cement the color to the surface, opaque underglazes are often added to the raw clay in one or more applications.
Opaque underglazes have the benefit of offering a wide variety of rich colors, which makes them a popular option for artists who wish to add strong, vivid color to their creations. They are a versatile material for a range of ceramic art applications since they can also be used to make beautiful designs and patterns.
The capacity of opaque underglazes can tolerate high temperatures and maintain stability during the glazing and firing process is another benefit. As a result of their resistance to fading, wear and tear, and discoloration, they are a great option for furniture that will be used on a regular basis.
Transparent Underglaze
This kind of underglaze is used on top of an opaque underglaze to give the colors more depth and radiance. A form of underglaze called transparent underglaze is used in ceramics to give a piece’s colors more depth and radiance. Transparent underglazes let the underlying clay to be seen, in contrast to opaque underglazes that totally cover the clay surface. This produces a distinctive, multi-layered look that gives the finished item depth and richness.
Underglazes that are transparent are often put on top of underglazes that are opaque, and the degree of transparency can be altered by varying the thickness of the application. They are normally applied in a number of thin layers, each of which is fired before the addition of the next. In doing so, the artist can produce a variety of subtle color effects and gradually build up the desired level of transparency.
Transparent underglazes are renowned for withstanding high temperatures as well, which makes them perfect for use in utilitarian ceramic items that will be used frequently. They are a durable and dependable material for artists because they are also resistant to fading, staining, and other types of deterioration.
Semi-transparent Underglaze
This kind of underglaze offers a blend of opaque and transparent color that lets the underlying clay shine through. A type of underglaze used in ceramic arts that combines solid and transparent color is called semi-transparent underglaze. This kind of underglaze creates a multi-layered look that gives the finished item depth and richness by allowing part of the underlying clay to shine through.
Typically, semi-transparent underglazes are put on top of opaque underglazes, and the thickness of the application can be changed to alter the degree of transparency. They are normally applied in several thin coats, each of which is fired before the addition of the following. In doing so, the artist can produce a variety of subtle color effects and gradually build up the desired level of transparency.
Semi-transparent underglazes are renowned for withstanding high temperatures as well, which makes them perfect for use in practical ceramic items that will be used frequently. They are a durable and dependable material for artists because they are also resistant to fading, staining, and other types of deterioration.
Liquid Underglaze
Underglaze that is liquid in consistency can be sprayed, brushed, or sponge-applied to the clay’s surface. It has a thin, liquid consistency. Underglaze with a thin, liquid viscosity is known as liquid underglaze and is utilized in ceramic arts. It offers a variety of colors and effects and is applied to the raw clay surface using a brush, sponge, or sprayer.
The simplicity of application of liquid underglaze is one of its benefits. It can be applied to the clay surface by brushing, sponging, or spraying, allowing for a range of techniques and results. Additionally, it is a well-liked option for artists that favor working with liquid materials.
Another benefit of liquid underglaze is how readily it layers and blends. This makes it the perfect option for artists who wish to produce elaborate drawings, complicated color schemes, and multi-layered effects.
The adaptability of liquid underglaze is another benefit. A variety of hues, from vivid and dramatic to subtle and clear, can be produced using it. Intricate patterns and motifs can be made by artists thanks to its suitability for precise details.
Dry Underglaze
This kind of underglaze is available as a dry powder that must first be diluted with water to resemble paint before being applied. Underglaze that is put to the surface of raw clay in a dry powder state is known as dry underglaze. It is a type of underglaze used in ceramic arts. To make a paste that may be applied to the clay surface, it is typically combined with a liquid binder, like water or a medium.
The simplicity of use of dry underglaze is one of its benefits. Artists may create a multitude of textures and effects by blending it to different consistencies. Additionally, it is simple to transport and store, making it a practical material for artists who operate in many locations.
Dry underglaze is renowned for its capacity to produce intense, vivid hues. It offers several different color possibilities, from vivid and strong to delicate and clear. It is therefore the perfect option for artists who want to add strong, vibrant color to their works.
The adaptability of dry underglaze is another benefit. A variety of textures, from smooth and glossy to rough and matte, can be produced using it. Intricate patterns and motifs can be made by artists thanks to its suitability for precise details.
The choice of underglaze type frequently depends on the desired outcome and the chosen fire procedure because each form of underglaze has distinctive qualities and application methods.
What Is A Colored Slip?
Ceramic artists employ a colored slip, which is a liquid concoction of clay, water, and colors. It can be used for both utilitarian and decorative functions and is applied to the clay object’s surface in a thin, even layer.
A homogeneous and consistent color on the pottery’s surface is one of the main advantages of colored slip. This is particularly helpful for establishing a base color or hiding any flaws in the clay surface.
Versatility is another another advantage of colored slip. It can be used on a range of surfaces, including glazed surfaces, bisque-fired clay, and raw clay. Additionally, a variety of effects, like solid color blocks and mottled and textured surfaces, can be produced using it.
Earthenware, stoneware, and porcelain clays can all be used to make colored slips, which can then be mixed and matched to produce a variety of hues. While some buy pre-made colored slips, other artists prefer to produce their own.
What Are Engobes?
Ceramic artists utilize engobes, which are a sort of colored slip. They are a thin, even layer of clay, water, and colours put to the surface of the clay piece. Engobes are similar to colored slips, but they are thicker and more paste-like in consistency since they are often more finely powdered and contain less water.
Engobes can be utilized both functionally and aesthetically. They can be used to produce a consistent and uniform color on the pottery’s surface, to hide any flaws in the clay’s surface, or to make elaborate patterns and designs.
Engobes’ superior adhesion to the clay’s surface is one of its main advantages. They are renowned for their capacity to create precise, distinct, and intricate designs, and they may be used on a range of surfaces, including raw clay, bisque-fired clay, or even glazed surfaces.
The clays used to make engobes, which can be formed to produce a variety of hues, include earthenware, stoneware, and porcelain. While some artists like to buy pre-made engobes, others prefer to create their own.
What Are The Ingredients In Glazes And Underglazes?
Depending on the type and desired characteristics of the glaze or underglaze, different components are used to create glazes and underglazes.
Ingredients In Glazes
- A form of glass that gives the glazing its fundamental structure.
- Mineral called alumina helps bind the glazing and gives it longevity.
- A specific kind of alkali that balances glazes and controls their melting temperatures.
- A kind of clay that aids in regulating the glaze’s viscosity and flow.
- The pigments that are added to the glaze to give it color, such as iron oxide or cobalt oxide.
Ingredients Underglazes
- The underglaze’s foundation is made of the fine-grained material clay.
- The pigments that are applied to the underglaze to give it color, such as iron oxide or cobalt oxide.
- A kind of glass that is mixed with underglaze to increase adhesion to the clay’s surface and regulate melting temperature.
- To thin the underglaze to the appropriate consistency, use water.
Feldspar, boron, or zinc are a few extra chemicals that some glazes and underglazes may include to enhance their performance and qualities. The specific type and desired attributes of a glaze or underglaze, as well as the materials and firing circumstances employed, will determine the precise ingredients used in the glaze or underglaze.
What Are Some Common Underglaze Techniques Used For Pottery Decoration?
Because they permit a broad spectrum of artistic expression and are relatively simple to apply, underglazes are a common media for pottery decorating. Here are a few typical underglaze decorating methods for pottery:
Brushwork
Using brushes, underglaze is applied directly to the clay object’s surface. This method is excellent for producing complex patterns, fine lines, and delicate details.
When decorating pottery, the brushwork technique is used to apply underglaze to the surface of the clay piece. This method is excellent for producing complicated designs, thin lines, and delicate details since it offers a high degree of control and precision.
With brushwork, the underglaze is diluted to a brushable consistency and then applied to the clay object’s surface using a range of brush types and sizes. To produce various effects and line widths, the artist can select from a wide variety of brush types, from flat brushes to liner brushes with fine tips.
From straightforward lines and patterns to intricate images and portraits, brushwork may be utilized to produce a broad variety of designs. To create even more complex and layered motifs, the method can be combined with other underglaze techniques like sponging or slip trailing.
Sponging
Applying underglaze to a clay object’s surface using a sponge. This method is frequently used to create backdrops and textures because it may produce an organic, textured look.
A sponge is used to add underglaze to the surface of a clay object as part of the spongeing pottery decoration method. This method is popular for producing backdrops and textures because it produces an organic, textured effect.
The underglaze is thinned to the proper sponging consistency before being applied to the clay object’s surface using a natural or synthetic sponge. To produce various textures and effects, the artist can utilize various sponge types, shapes, and pressures.
From straightforward dots and dashes to more intricate designs, a variety of textures and patterns may be produced using sponges. To create even more complex and multi-layered designs, the method can be coupled with other underglaze techniques like brushwork or slip trailing.
Slip Trailing
Applying underglaze continuously with a slip trailer or squeeze bottle to create lines and patterns. For making lines, borders, and recurring patterns, this method works well.
Using a slip trailer or squeeze bottle, underglaze is applied to the surface of a clay piece to decorate pottery using the slip trailing process. This method is excellent for drawing lines and designs since it offers a great degree of control and precision.
Slip trailing involves thinning the underglaze to a trailing-appropriate consistency before applying it to the surface of the clay piece in a continuous stream using a slip trailer or squeeze bottle. To produce various line widths and effects, the artist can utilize various nozzle sizes, shapes, and pressures.
From straightforward lines and borders to more intricate patterns and shapes, slip trailing can be used to produce a variety of designs. To create even more complex and layered motifs, the method can be coupled with other underglaze techniques like brushwork or sponging.
Stamping
Applying underglaze to the surface of a clay piece by stamping. This method is frequently used to produce recurring patterns and designs and can be used in conjunction with other underglaze methods to produce results that are more complicated.
Using a stamp, underglaze is applied to the surface of a clay piece to decorate pottery using the stamping process. This method is excellent for constructing patterns and designs since it provides for a high level of reproducibility and consistency.
When utilizing stamping, the underglaze is thinned to the proper stamping consistency and then applied to the clay object’s surface using a carved or molded stamp. To achieve various effects, the artist can choose from a variety of stamps, ranging from straightforward shapes to intricate designs.
From straightforward dots and lines to more intricate motifs and designs, stamping may be used to produce a broad variety of patterns. To create even more complex and layered motifs, the method can be coupled with other underglaze techniques like brushwork or sponging.
Screen Printing
Applying underglaze to the surface of a clay piece while using a stencil and screen. This method is perfect for producing intricate and repetitive designs and is frequently utilized in industrial settings.
A screen and a squeegee are used to apply underglaze to the surface of a clay piece in the screen printing method of pottery decorating. This method is excellent for producing intricate and detailed designs and is frequently utilized for mass production.
Using a stencil and a squeegee, screen printing involves thinning the underglaze to a consistency appropriate for screen printing and applying it to the clay object’s surface. The underglaze is applied to the clay sculpture through a screen that has the stencil on it.
Simple patterns and logos to more intricate pictures and designs can all be produced with screen printing. The method’s high degree of reproducibility and precision make it perfect for large-scale manufacturing.
The use of underglaze with screen printing necessitates specific tools and knowledge, and is usually reserved for mass production as opposed to artisanal or small-scale work.
Sgraffito
The process of scratching away an underglaze to reveal the clay body beneath. This method, which can add texture and contrast, is frequently used to make patterns and designs.
Sgraffito is a pottery decorative method that includes cutting into an underglaze or slip layer to expose the underlying clay body. This method is perfect for producing elaborate and detailed designs since it produces a great level of contrast and depth.
Sgraffito involves applying underglaze or slip to the clay object’s surface and letting it dry. The artist then carves into the layer with a sharp object, such a needle or a blade, exposing the clay body beneath. A variety of designs, from straightforward patterns and images to more intricate ones, can be made using the carved lines.
Sgraffito can be used in conjunction with other underglaze methods like brushwork or sponging to produce even more complex and multi-layered motifs. To provide even more depth and contrast, it’s also possible to use several layers of underglaze or slip, each with a different design.
Underglaze Pencils for Pottery
The ceramic marking tool known as an underglaze pencil is used to decorate ceramics before it is fired. These pencils are made from a blend of fine clay and colored pigments that has been shaped into the shape of a pencil. Although they are made expressly for use on ceramic surfaces, they are utilized in a manner similar to graphite or charcoal pencils.
Using underglaze pencils is a practical and adaptable approach to decorate ceramics with elaborate and detailed motifs. They can be employed to produce text, outlines, shading, and a variety of other ornamental effects. They are perfect for putting text or numbers to ceramics as well as for drawing precise lines and embellishments.
Underglaze pencils have the benefit of being able to be used on both greenware and bisque-fired clay, and once dry, they won’t smear or smudge. Additionally, they are water-soluble, making it simple to mix or remove them with a moist brush or sponge.
TIP: Before beginning a bigger project, I recommend to test the colors on a tiny piece of bisque or greenware because when using underglaze pencils, the colors will shift and darken during firing. Additionally, it’s critical to keep in mind that the sort of glaze or underglaze that is applied on top can impact the colors, as can the kiln’s temperature and atmosphere.
Underglaze pencils can be covered with a layer of clear glaze or underglaze before firing in order to guarantee that the colors stay true and bright. This will lessen the chance of color fading or bleeding during fire.
How Is Greenware or Bisque Surface Prepared Before Painting With An Underglaze?
An essential stage in the creation of pottery is to prepare the surface of a piece of greenware or bisque before painting it with an underglaze because this decision impacts the object’s ultimate appearance and durability. I recommend you follow the following procedures for getting a greenware or bisque surface ready for underglazing:
- I recommend to remove any dirt, dust, or oil from the greenware or bisque surface before applying the underglaze. A gentle cloth or brush and warm, soapy water can be used for this.
- Sand the surface: Sanding the surface makes it easier for the underglaze to adhere to a smooth, level surface. The surface should be carefully sanded in a circular motion using fine-grit sandpaper or a sanding sponge.
- Applying a primer to the greenware or bisque surface will improve the underglaze’s adhesion and help to produce a base color that is more uniform.
- After applying the primer, it’s crucial to wait until the surface is totally dry before adding the underglaze.
- The underglaze can be applied using the preferred method, such as brushing, sponging, or stamping, once the surface has been ready and has completely dried.
After Decorating A Fired Clay Piece With An Underglaze, What Happens Next In The Process Of Creating A Finished Product?
The process of turning burned clay into a finished item continues with the application of glaze after the piece has been decorated with an underglaze. Over the underglaze, the glaze is a thin, transparent or opaque coating made of melted glass or ceramic material. The glaze enhances the underglaze’s appearance and color in addition to adding a protective covering to the object.
The steps in the glazing process are as follows:
- Before glazing, it’s vital to clean the piece’s surface to get rid of any dust, debris, or grease that could prevent the glaze from adhering.
- Glaze can be prepared by combining glaze powder with water to the proper consistency, or it can be purchased already mixed. To guarantee an even application, the glaze needs to be properly mixed.
- You can either brush, dip, or pour the glaze on. Applying the glaze evenly is essential to prevent air bubbles from affecting the piece’s final appearance.
- Give the piece time to completely dry after glazing. Setting it alone for a few hours or overnight will do this.
- To further reinforce and firm the clay body and set the glaze, the piece is burnt in a kiln a second time, at a lower temperature than the initial firing, known as a “bisque fire.”
- The item is prepared for the final glaze firing after the bisque firing. The glaze’s shiny, translucent appearance is a result of this firing, which is carried out at a temperature higher than the bisque firing.
- The object is cooled and taken out of the kiln following the fire of the final glaze. The finished item should be a stunning piece of pottery that is strong and has a glossy, smooth surface.
Does It Matter Where The Decorated Pieces Are Placed On Kiln Shelves During Firing?
When utilizing an underglazing process, it concerns where the decorated pieces are set on the kiln shelves during firing. Particularly in terms of color and pattern consistency, the order in which the pieces are placed in the kiln might influence the outcome.
There are many things to think about.
Kilns are made to distribute heat equally, however the arrangement of the items inside the kiln can still have an impact on how the heat is dispersed. Pieces positioned close to the kiln’s elements or walls frequently encounter more heat and cool more quickly than those positioned in its center.
Different underglaze colors may react to heat in different ways, resulting in changes to color intensity, shading, or streaking. To reduce color fluctuations, it’s critical to group like hues together.
Consistency in design: Sgraffito is one underglaze technique that is sensitive to the direction of heat flow in the kiln. It can be easier to achieve consistent results by grouping items with comparable designs together.
The amount of oxygen present during the fire process in particular can have an impact on the outcome. Consistent outcomes can be achieved by arranging the pieces in the kiln to reduce the mixing of various atmospheres.
Is There Anything Special About Preparing Bisque-Fired Clay For Use With An Underglazing Technique?
When preparing bisque-fired clay for use with an underglazing process, there are a few unique considerations. Clay that has been burned once to a temperature high enough to make it robust and porous but has not yet vitrified, or completely melted and hardened, is referred to as being “bisque-fired.” Because it produces a surface that is responsive to the underglaze substance, which will penetrate into the pores of the clay and cling nicely to the surface, bisque is perfect for underglazing.
For usage with an underglaze, bisque-fired clay must be properly prepared.
Thoroughly clean the surface since dirt, dust, or any other leftovers may prevent the underglaze from adhering. It’s crucial to scrub the bisque’s surface thoroughly with a damp sponge or towel.
If necessary, lightly sand the bisque’s surface to remove any ridges or bumps that might obstruct the underglaze application.
Before applying the underglaze, you can give the bisque a smoother surface so that it will stick to it better and to stop the underglaze from soaking into the porous bisque too deeply by applying a thin coating of clear glaze or a sealer.
It’s crucial to give the bisque enough time to dry completely before putting on the underglaze. This will aid in preventing surface runoff or pooling of the underglaze.
Different kinds of bisque may have varying degrees of porosity, which may have an impact on the outcome when applying an underglaze. To make sure that the underglaze will attach well and give the desired results, it is best to test the bisque with a little piece before beginning a larger job.
FAQs: Exploring the Contrasts Between Glaze and Underglaze
We know you’re curious about the differences between glaze and underglaze, so we’ve put together this FAQ to answer your burning questions!
Q: What is the difference between glaze and underglaze? A: Ah, the age-old question! In simple terms, glaze is a coating that is applied to a ceramic piece to create a glassy, waterproof surface, while underglaze is a decorative technique that involves applying colored pigments to the surface of the ceramic piece before it is glazed. Underglaze creates a matte finish, while glaze creates a shiny finish.
Q: Can you use glaze and underglaze together? A: Absolutely! Many ceramic artists use a combination of glaze and underglaze to create stunning effects on their pieces. You can apply underglaze to a piece, let it dry, and then apply glaze over the top to create a glossy finish.
Q: What are the benefits of using underglaze? A: One of the biggest benefits of using underglaze is the ability to create intricate designs and patterns on your ceramic pieces. Unlike glaze, which can be difficult to control and may run during firing, underglaze stays put where you apply it. It also dries quickly and can be layered to create depth and texture.
Q: Why do some artists prefer glaze over underglaze? A: Glaze is a popular choice for many artists because it creates a glossy, reflective surface that enhances the colors of the ceramic piece. It is also waterproof and helps protect the piece from damage. However, glaze can be difficult to control and may require multiple coats to achieve the desired effect.
Q: Can you mix different glazes and underglazes together? A: Yes, you can! However, it’s important to keep in mind that different glazes and underglazes may react differently during firing, so it’s always a good idea to test your combination on a small piece before using it on a larger project.
We hope these answers have helped you better understand the contrasts between glaze and underglaze. Don’t be afraid to experiment and have fun with these versatile techniques!
Ceramic Artist That Have Taken Underglazes To The Next Level
Beatrice Wood
Beatrice Wood was an American potter and studio artist who specialized in using underglazes in her pottery. She was a pro at sgraffito, and her works are highly prized for their elaborate patterns and vivid hues.
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