When a functional surface for food and drink isn’t a concern, the possibilities for rough, matte, imperfect, or otherwise sculptural fired finishes are endless. Below is a unique approach to terra sigillata.
When the desired end result of terra sigillata is no longer a highly burnished, watertight surface, new possibilities open up for terra sigillata applications and uses. And while using terra sigillata certainly involves various risks, it equally encompasses
enormous potential. This includes unconventional colorants, such as commercial underglaze inclusions and an expanded color palette. Applying terra sigillata after the bisque firing and in combination with flux washes and slips with flux additives
expands the possibilities of when and how a terra sigillata can be applied. Layering terra sigillata with wash materials, patinas, and cold-surface materials expands the variety of final surfaces you can create.
Perceived flaws, such as flaking and cracking, hold potential to enhance a terra sigillata surface. Terra sigillata can be mixed and used thicker than normal to create a thick, waxy coating on a form; its reactivity with glazed surfaces potentially makes
wrinkle-like textures. And terra sigillata, with its root as a clay slip, can be used to dip and coat a form, like that seen in the contemporary practice of slip-dipping forms.
Expanding any material beyond traditional use requires risk, ingenuity, and intuition. Even with terra sigillata’s long history, the ability to see beyond what is traditional allows for new advancements and offers many alternative possibilities.
As with all experiments, recording the process and changes make the results repeatable for further explorations.
Flaking
Aside from the unfired clay form cracking during the application process, flaking is another common issue faced when working with terra sigillata. Granted, there are times when you want the perfect waxy coating that terra sigillata traditionally
creates, but the flaking can also be used in an advantageous way. More than likely if the terra sigillata does unintentionally flake away from your piece, or if you are specifically seeking the flaking quality of terra sigillata, you will want to
find a way to stabilize or stop this process from further flaking after the final firing. An effective way to remove the loose terra sigillata flakes, while maintaining the integrity of the surface, involves scrubbing it with wet/dry sandpaper.
Sanding Terra Sigillata
Submerge the piece, or the area of the piece you are working on under water (1, 2). Gently scrub the piece with 600- or 800-grit wet/ dry sandpaper to remove the flaking terra sigillata (3). If your piece is non-utilitarian (not intended for food use),
you can leave the sanded terra sigillata surface as is after the sanding process (4, 5). If your piece is intended for food use or you prefer a sealed surface, you can apply a layer of glaze to further stabilize the flaking texture (6).
1 Submerge the bowl form in water or alternatively hold it under running water.2 Gently sand the surface of bowl with 600-grit wet/dry sandpaper until all loose flakes have been removed.
3 The sanded surface looks weathered and reveals the darker terra sigillata layer below.4 A sanded surface that has been covered with a soda ash wash and lithium carbonate wash layer to stabilize any further flaking, which also creates a weathered surface. This piece was made from earthenware and fired to cone 03 in an electric kiln.
5 A flaking white terra sigillata surface that has been sanded to remove any loose terra sigillata.6 Apply a clear glaze over the flaked surface to seal it and create a food-safe surface.
7 White terra sigillata flaking off after the initial firing in an electric kiln with stained terra sigillata layered underneath.
Cracking
When you open a kiln only to discover an unexpected crack in your piece, you likely feel disappointment and frustration, especially if that crack formed after your piece successfully survived the drying process. An inadvertent consequence of too
much lithium carbonate wash or a highly concentrated application of lithium carbonate in its raw form, is cracking on thinly constructed forms. In my own work, this over-zealous application has damaged a handful of delicate handbuilt works, and despite
this, I can envision potential with this result. Further experimenting would need to be completed to determine if this cracking effect can or does happen on thicker forms as well.
8 Cracking caused from too much lithium carbonate wash on a thin form.
Excerpted and adapted from Terra Sigillata: Contemporary Techniques by Rhonda Willers. This book is available in the Ceramic Arts Network Shop at ceramicartsnetwork.org/shop.
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When a functional surface for food and drink isn’t a concern, the possibilities for rough, matte, imperfect, or otherwise sculptural fired finishes are endless. Below is a unique approach to terra sigillata.
When the desired end result of terra sigillata is no longer a highly burnished, watertight surface, new possibilities open up for terra sigillata applications and uses. And while using terra sigillata certainly involves various risks, it equally encompasses enormous potential. This includes unconventional colorants, such as commercial underglaze inclusions and an expanded color palette. Applying terra sigillata after the bisque firing and in combination with flux washes and slips with flux additives expands the possibilities of when and how a terra sigillata can be applied. Layering terra sigillata with wash materials, patinas, and cold-surface materials expands the variety of final surfaces you can create.
Perceived flaws, such as flaking and cracking, hold potential to enhance a terra sigillata surface. Terra sigillata can be mixed and used thicker than normal to create a thick, waxy coating on a form; its reactivity with glazed surfaces potentially makes wrinkle-like textures. And terra sigillata, with its root as a clay slip, can be used to dip and coat a form, like that seen in the contemporary practice of slip-dipping forms.
Expanding any material beyond traditional use requires risk, ingenuity, and intuition. Even with terra sigillata’s long history, the ability to see beyond what is traditional allows for new advancements and offers many alternative possibilities. As with all experiments, recording the process and changes make the results repeatable for further explorations.
Flaking
Aside from the unfired clay form cracking during the application process, flaking is another common issue faced when working with terra sigillata. Granted, there are times when you want the perfect waxy coating that terra sigillata traditionally creates, but the flaking can also be used in an advantageous way. More than likely if the terra sigillata does unintentionally flake away from your piece, or if you are specifically seeking the flaking quality of terra sigillata, you will want to find a way to stabilize or stop this process from further flaking after the final firing. An effective way to remove the loose terra sigillata flakes, while maintaining the integrity of the surface, involves scrubbing it with wet/dry sandpaper.
Sanding Terra Sigillata
Submerge the piece, or the area of the piece you are working on under water (1, 2). Gently scrub the piece with 600- or 800-grit wet/ dry sandpaper to remove the flaking terra sigillata (3). If your piece is non-utilitarian (not intended for food use), you can leave the sanded terra sigillata surface as is after the sanding process (4, 5). If your piece is intended for food use or you prefer a sealed surface, you can apply a layer of glaze to further stabilize the flaking texture (6).
Cracking
When you open a kiln only to discover an unexpected crack in your piece, you likely feel disappointment and frustration, especially if that crack formed after your piece successfully survived the drying process. An inadvertent consequence of too much lithium carbonate wash or a highly concentrated application of lithium carbonate in its raw form, is cracking on thinly constructed forms. In my own work, this over-zealous application has damaged a handful of delicate handbuilt works, and despite this, I can envision potential with this result. Further experimenting would need to be completed to determine if this cracking effect can or does happen on thicker forms as well.
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