Zöldverdigris

Zöldverdigris is a colloquial Hungarian term referring to the green patina that forms on copper and brass surfaces. This greenish layer is a result of oxidation and the reaction of the metal with environmental elements such as moisture, air, and pollutants. Chemically, verdigris is a complex mixture of copper salts, primarily copper carbonates and acetates, though chlorides and sulfates can also be present depending on the environment.

The formation of zöldverdigris is a natural process that occurs over time. In outdoor settings, exposure to rain and atmospheric conditions accelerates its development. Indoors, humidity and the presence of certain chemicals can also contribute. While often associated with the aging of copper objects like statues, roofs, and antique cookware, it can also be an undesirable byproduct on newly manufactured brass items if not properly protected.

Historically, the term verdigris has also been used to describe a pigment derived from this natural patina. This pigment was historically produced by exposing copper sheets to acetic acid vapors, often in the presence of fermented grapes or urine, to create copper acetates. However, the natural patina on metal objects is a more common understanding of zöldverdigris today. The appearance of zöldverdigris can range from a light turquoise to a deep blue-green, and its texture can vary from powdery to a hard, encrusted layer.