Eosin
Many Zsolnay ceramics are noted for the use of the eosin process that was introduced in 1893. The process results in a light red iridescence of the first prepared hue, hence the term eosin (Greek eos, flush of dawn). Different eosin colours and processes were developed over time. The eosin-based iridescence became a favourite of art nouveau and Jugendstil artists, among them Sándor Apáti Abt, Lajos Mack, Géza Nikelszky, and József Rippl-Rónai.
The secret eosin glaze renders porcelain to appear iridescent metallic, in different colours that change with the angle of reflection. Typical colours include shades of green, red, blue, and purple.
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