Using terra sigillata to color and seal wares is an ancient technique. But as Rhonda Willers explains, the traditional terra sigillata technique—applying to bone-dry ware and burnishing—is just one option among many. When the classic burnished sheen and water-tight surface aren't the goal, there are endless ways to use terra sigillata to express your vision.
In this post, an excerpt from the September/October 2026 issue of Pottery Making Illustrated, Rhonda breaks down the variables that shape how terra sigillata behaves and looks. She also shares some ways you can exploit those variables to create beautiful surfaces! –Jennifer Poellot Harnetty, editor
In the past, deciding when and how to apply terra sigillata was rather fixed; one must apply it before the bisque firing, and it should be burnished between layers. If a historically inspired use of terra sigillata is desired, then the application process should follow traditional approaches. Presently, the use of terra sigillata expands beyond the traditional method—when the burnished sheen and water-tight qualities are unnecessary, terra sigillata can be used for its waxy, skin-like coating, making an effective base surface that highlights sensitive mark making created during the object’s forming stages.
Because of the fine particle size and lack of a fusing layer, terra sigillata, when used alone, best adheres to the clay body when applied before the bisque firing. However, terra sigillata can be applied after the bisque firing or after multiple firings, but different processes and materials are needed to successfully adhere the terra sigillata to the form.
Other considerations for application include: surface qualities, structure and scale of the piece, and overall fragility of the unfired piece.
Leather Hard and Bone Dry
Applying terra sigillata by brushing or dipping at the leather-hard state naturally encourages, or creates, a waxy burnished-like sheen without the burnishing process. However, because there is elevated moisture content in the clay, the terra sigillata sits on the surface rather than being absorbed by the clay surface. This results in a less opaque covering of terra sigillata. This could be an interesting application when a semi-translucent layering effect is desired.
At the bone-dry state, when clay is the driest before the bisque firing, the brushed or dipped terra sigillata is more deeply absorbed into the clay’s outer surface, allowing more layers of terra sigillata to be built up, thereby creating a more uniform and opaque surface. This stage of clay is also when the clay is at its most fragile state, and care must be given when applying the terra sigillata.
How Many Layers?
Traditional terra sigillata application process advises no more than three brushed layers of terra sigillata be applied, otherwise flaking and peeling become more likely after the bisque firing. This suggestion assumes the terra sigillata has a specific gravity of 1.15.
If the terra sigillata is thinner, with a specific gravity of 1.10, more layers will need to be applied to reach an opaque surface or to create visual depth with multiple colored layers. With a more watery composition, single brushed on layers of terra sigillata will result in translucency, which is both potentially disappointing or advantageous depending on your goals for the surface of your piece.
Conversely, if the specific gravity is closer to 1.20, then fewer layers should be applied to avoid peeling terra sigillata.
Application for Translucent Effects
The translucent quality of terra sigillata can be used to your advantage in a variety of ways. Often, terra sigillatas appear very flat because of their opaque, flat nature. Thinner application layers allow a depth of color to be created by allowing colors from below to filter through layers above.
Timing and Pace of Application
Because terra sigillata is often applied at the most fragile state of clay, bone dry, it is important to consider the overall fragility of your piece. To avoid cracking in the application process, aim to apply the terra sigillata as quickly and as evenly as possible, regardless of the application method (brush, dip, or spray). Thinner clay forms are at greater risk of cracking during the terra sigillata application process. If one area of the piece becomes over-saturated with terra sigillata, it will likely cause cracking in the piece due to the difference in moisture content throughout the piece. In your beginning stages of working with terra sigillata, consider practicing the application process on pieces of lesser preciousness.
Search the Daily
Published Sep 7, 2026
In this post, an excerpt from the September/October 2026 issue of Pottery Making Illustrated, Rhonda breaks down the variables that shape how terra sigillata behaves and looks. She also shares some ways you can exploit those variables to create beautiful surfaces! –Jennifer Poellot Harnetty, editor
PS. To see how Rhonda uses soft- versus stiff-bristled brushes, check out her full article in the September/October 2026 issue of Pottery Making Illustrated. Not a subscriber? Subscribe today!
In the past, deciding when and how to apply terra sigillata was rather fixed; one must apply it before the bisque firing, and it should be burnished between layers. If a historically inspired use of terra sigillata is desired, then the application process should follow traditional approaches. Presently, the use of terra sigillata expands beyond the traditional method—when the burnished sheen and water-tight qualities are unnecessary, terra sigillata can be used for its waxy, skin-like coating, making an effective base surface that highlights sensitive mark making created during the object’s forming stages.
Because of the fine particle size and lack of a fusing layer, terra sigillata, when used alone, best adheres to the clay body when applied before the bisque firing. However, terra sigillata can be applied after the bisque firing or after multiple firings, but different processes and materials are needed to successfully adhere the terra sigillata to the form.
Other considerations for application include: surface qualities, structure and scale of the piece, and overall fragility of the unfired piece.
Leather Hard and Bone Dry
Applying terra sigillata by brushing or dipping at the leather-hard state naturally encourages, or creates, a waxy burnished-like sheen without the burnishing process. However, because there is elevated moisture content in the clay, the terra sigillata sits on the surface rather than being absorbed by the clay surface. This results in a less opaque covering of terra sigillata. This could be an interesting application when a semi-translucent layering effect is desired.
At the bone-dry state, when clay is the driest before the bisque firing, the brushed or dipped terra sigillata is more deeply absorbed into the clay’s outer surface, allowing more layers of terra sigillata to be built up, thereby creating a more uniform and opaque surface. This stage of clay is also when the clay is at its most fragile state, and care must be given when applying the terra sigillata.
How Many Layers?
Traditional terra sigillata application process advises no more than three brushed layers of terra sigillata be applied, otherwise flaking and peeling become more likely after the bisque firing. This suggestion assumes the terra sigillata has a specific gravity of 1.15.
If the terra sigillata is thinner, with a specific gravity of 1.10, more layers will need to be applied to reach an opaque surface or to create visual depth with multiple colored layers. With a more watery composition, single brushed on layers of terra sigillata will result in translucency, which is both potentially disappointing or advantageous depending on your goals for the surface of your piece.
Conversely, if the specific gravity is closer to 1.20, then fewer layers should be applied to avoid peeling terra sigillata.
Application for Translucent Effects
The translucent quality of terra sigillata can be used to your advantage in a variety of ways. Often, terra sigillatas appear very flat because of their opaque, flat nature. Thinner application layers allow a depth of color to be created by allowing colors from below to filter through layers above.
Timing and Pace of Application
Because terra sigillata is often applied at the most fragile state of clay, bone dry, it is important to consider the overall fragility of your piece. To avoid cracking in the application process, aim to apply the terra sigillata as quickly and as evenly as possible, regardless of the application method (brush, dip, or spray). Thinner clay forms are at greater risk of cracking during the terra sigillata application process. If one area of the piece becomes over-saturated with terra sigillata, it will likely cause cracking in the piece due to the difference in moisture content throughout the piece. In your beginning stages of working with terra sigillata, consider practicing the application process on pieces of lesser preciousness.
Learn more about terra sigillata in Rhonda Willers’ book, Terra Sigillata: Contemporary Techniques, published by The American Ceramic Society and available in the Ceramic Arts Network shop at ceramicartsnetwork.org/shop.
Unfamiliar with any terms in this article? Browse our glossary of pottery terms!
Related Content
Ceramic Artists
Functional Pottery
Ceramic Sculpture
Glaze Chemistry
High-Fire Glaze Recipes
Mid-Range Glaze Recipes
Low-Fire Glaze Recipes
Ceramic Colorants
Ceramic Glazes and Underglazes
Ceramic Raw Materials
Pottery Clay
Ceramic Decorating Tools
Ceramic Kilns
Making Clay Tools
Wheel Throwing Tools
Electric Kiln Firing
Gas Kiln Firing
Raku Firing
Salt Firing and Soda Firing
Wood Kiln Firing
Ceramic Decorating Techniques
Ceramic Glazing Techniques
Handbuilding Techniques
Making Ceramic Molds
Making Ceramic Tile
Wheel Throwing Techniques