AMACO Blue Starlight with Cobalt Celadon by Kelsey Schroeder

What it is

AMACO Blue Starlight with Cobalt Celadon is a midfire glaze combination from the Cosmos series, designed for firing at cone 5–6. It belongs to a group of reactive surfaces that develop a crystalline-like pattern without extended soak times or complex firing schedules. Unlike traditional high-fire crystalline systems, AMACO Blue Starlight with Cobalt Celadon forms its character within a standard cone 6 firing cycle, relying on glaze interaction rather than kiln manipulation.

The surface reveals a deep blue field layered with lighter formations that read like a night sky. These “stars” emerge through localized crystallization and phase separation within the glaze, enhanced by the presence of cobalt celadon beneath or alongside it. The finish remains glossy, with depth that shifts across the form, especially where the two glazes meet and respond to thickness and heat.

Application and firing behavior

Blue Starlight responds clearly to thickness.

• Heavier application (2–3+ coats) encourages more pronounced crystalline development, with visible light bursts and halo-like edges.
• Thinner application (1 coat) results in a more even blue surface with minimal patterning.

The glaze interacts strongly with form. It tends to activate on shoulders and pooling areas, while remaining calmer on lower, thinner sections. With excessive thickness, slight movement can occur during firing, so controlled application is important, especially on vertical surfaces.

At cone 6 (≈1220°C), the glaze matures reliably and produces its characteristic surface without controlled cooling cycles. Slower cooling can subtly enhance the definition of crystalline features, though results remain stable in a standard kiln schedule.

Compatibility and combinations

Blue Starlight is often used in layered applications, particularly with:

• transparent or semi-transparent celadons such as Cobalt Celadon, which add depth and tonal variation;
• satin or matte glazes, creating contrast in surface quality;
• tapered (gradient) applications, where variation in thickness produces a full range of effects.

When layered over or under other glazes, it can increase surface activity, so testing is recommended. Results also vary with clay body:

• on light stoneware, the pattern appears clearer and brighter;
• on darker bodies, the surface reads deeper and more subdued.

Blue Starlight demonstrates how midfire glazes can deliver complex, crystalline surfaces without demanding firing processes. It offers both control and variability, responding directly to thickness, placement, and form. Within the Cosmos series, it stands as a practical approach to achieving layered, dimensional surfaces at cone 6, with results shaped as much by application as by the kiln.

Our favorite ceramic artist Kelsey Schroeder created a stunning example by combining AMACO Blue Starlight with Cobalt Celadon on Sheffield Pottery T6B stoneware (cone 6). The result is both controlled and full of life.

The strong cobalt celadon on the neck forms a deep, defined collar, while the tapered application of Blue Starlight across the body opens into a softer, star-filled surface. Where the glaze builds, crystalline patterns emerge clearly; where it thins, the blue lightens and breathes. The transitions feel natural, shaped by heat and movement in the kiln.

This piece shows how a thoughtful pairing of glazes, combined with careful control of thickness, can produce a rich, layered surface in a standard cone 6 firing—no complex schedules, just precision in application and a clear understanding of how the materials respond.