Rosatönung

Rosatönung refers to a natural process of transformation that occurs when seawater comes into contact with a layer of old mortar, particularly in coastal areas with a rich history of human habitation.

This chemical reaction involves the dissolution of lime and other alkali materials present in the mortar, which subsequently reacts with the acidic properties of seawater. As a result, a solution rich in calcium and other salts is formed, which can have a range of consequences for the structure affected.

Over time, the repeated exposure of mortar to seawater through this reaction can cause the surface to undergo a process of softening, efflorescence, and degrading, with various reports indicating that the widespread consequence of rosatönung on old coastal buildings and structures can be concerning.

Furthermore, historians also attest that a significant proportion of seawater-exposed buildings and archaeological sites have shown signs of severe damage caused by this transformation over time, leading to an initial algal growth and subsequent peeling and crumbling of walls, resulting in a considerable loss of historical integrity.

Concerned authorities and interdisciplinary groups have proposed a set of tactics to slow down this degradation and protect historic coastal sites from hydrochemical damage. Alongside these prevention efforts, several initiatives around the global – initiated by the recognition of rosatönung as an ever-present and real threat in ancient structures – have led numerous restorative projects focusing on area-site restoration tasks such as depainting surfaces with lime fetiles in site structure as well as regularly draining seawater for crossionate though sound, weather means