The Development of Pewabic's Iridescent Glazes

A display of Pewabic vessels in the newest addition to our Iridescent glaze collection, Azurite

Co-Founder Mary Chase Perry Stratton’s interest in glaze formulation was inspired in part by American industrialist and friend Charles Lang Freer. Freer championed and collected Mary’s work, challenging her to replicate the luster of vessels brought back from his travels to Persia and China.

 Portrait of Charles Lang Freer, 1919 from The National Portrait Gallery, Smithsonian Institution

After four years of experimentation with metal oxides and atmospheric firings, Pewabic’s first official Iridescent glazes were born.

Mary recounts the forty-two trials of a single glaze option it took to leave an impression on notable Finnish-American architect and designer Eero Saarinen in a letter to her friend Ella Peters in 1940.

“The degree of experiment can be realized from the fact that the glaze that pleased Mr. Saarinen was my forty-second trial in that particular color.” 

Mary Chase Perry Stratton and the Revelation Kiln late 1800s - early 1900s

The hard work paid off as Mary continued to develop her craft after learning from the masters. She writes, “... it is from the experts in these fields that I have received the greatest friendship and encouragement which, of course, is one of the most satisfactory experiences of my life.” Pewabic was not the only pottery producing vibrantly mirrored pots in the Western world–– Mary notes, “My glazes are based on well known formulas which are well within the reach of anyone. These are modified from experiment till I have made them my own.”

Portrait of Mary Chase mixing glaze elements circa 1940

Mary’s trailblazing spirit earned her honorary degrees from the University of Michigan and Wayne State University, “...mainly from the qualities beyond the usual in the various uses of my Iridescent glazes.” Her approach to Iridescent glaze formulation cemented Pewabic as a major force in the ceramic world during that time. 

The means of production have morphed over time as new information regarding the impact on health and safety come to light. For a pottery over a century old, many of the ingredients used during Mary’s exciting first experiments are prohibited from use today. These original ingredients included lead, and in some instances, uranium.

Pewabic glaze sample test circa 1930 with orange, uranium-glazed centers

A majority of the ceramic processes have remained consistent to the early days of Pewabic, but our glaze developers were tasked with getting creative in order to maintain that signature lustrous surface on modern vessels. Continuing Mary Chase’s legacy, we safely produce a curated selection of Iridescent glazes. Our “standard” glazed pieces go through two firings–– an initial bisque firing followed by another after glaze application. Iridescent pots require a third firing and process referred to as “fuming”, where vegetable oil is injected into the kiln, causing a metallic-like flash on the surface of the vessel. 

Present-day Glaze Development Specialist Alex hand-painting a custom piece

While the formulation of these glazes has changed over time, the high variation between pieces in the same glaze family is consistent with early notes from Mary Chase. In 1940 she wrote that the results were “...always uncertain but less so each time”. This still rings true to this day, as you can see in the variation of outcomes demonstrated in the photo below. 

 Medium Classic Vases in our Copper Iridescent glaze with two very different results

Tile depiction of the prophet Malachi surrounded by Iridescent accent tiles at the Basilica of the National Shrine of the Immaculate Conception in Washington, DC.

 A historic Pewabic residential fireplace

An Iridescent bedroom fireplace from our Design Portfolio  

Mary Chase was no stranger to trial and error, and we embrace glaze experimentation with the same curiosity. The inconsistencies that express themselves on the surface perfectly capture the spirit of an organization that does not shy away from appearing handmade. It is that exact human element that ties us indelibly to our craft.

Various Copper Iridescent vases from our collection–– "Petite" vases can only be purchased in-store or during special online releases 

We strive to create one-of-a-kind vessels and tiles to serve as heirlooms or help recount cherished memories for years to come. Mary had a creed that aligns with our mission today. It was that: “The object (has) to be handmade, made from the heart, and designed as a whole in proportion, shape, texture and use.” Our hope is that the work and the creative efforts of our vessel makers, designers, and glaze developers help keep the tangible art of handcraft alive.