Surface stratigraphy on limestone of venetian palaces

The surfaces of Venetian palaces are a testimony to a long history of maintenance. Documents from nineteenth-century restoration projects assign dates and reveal some reasons for treatments explaining, for example, the use of aggressive cleaning and then the addition of pigments so that the newly restored fa̧ade did not appear 'too white'. Restoration during the twenty-first century has presented the opportunity to study the stone surface of three palaces and their stratigraphy. Three types of layers were identified (pollution deposit, silica/wax treatment and corrosion) which overlay the original stone and show distinct elemental signatures. The texture of the outermost deposit showed that the particle size was greatest when it was derived from areas of greatest exposure to the wind compared with calmer sheltered parts. Waxy treatment layers contained strata that probably derived from the brush used to apply the treatment. These treatment layers were warmer in tone than the superficial deposit or underlying stone. Improved understanding of the stratigraphy can inform decisions as to what layers should be protected during restoration.