Green and gold Eosin Zsolnay ceramic spaniel. Many Zsolnay Porcelain Factory ceramics are noted for the use of the eosin process 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 colors were developed over time. The secret glaze renders porcelain to appear iridescent metallic in different colors that change with angle of reflection.