Block title

 Acidic residue of rain water remains on a reactive surface.

Description

Walls exhibit, overall deep adherent patination. Although the acidity of rain in the eastern US is generally high, rain by itself is not sufficient to corrode copper in this manner. This reaction occurs when the acidic residue of rain water remains on a reactive surface; dissolved by dew and other conditions that don't sufficiently dilute the acids or there is a persistent generation of sulfides in the atmosphere causing rapid patination. .