Natural and synthetic consolidants for earth heritage: a review

Abstract

Since ancient times, natural products have been used to preserve earthen structures. Old recipes with cactus resin, bee wax, or linseed oil, have passed through generations and, in some countries, are still used nowadays. On the other hand, 20th and 21st centuries brought synthetic products as a solution to restore and conserve historical buildings. Although these synthetic products were extensively studied for stone-based monuments, they are also being used in earth heritage. The act of consolidating a degraded surface is, in conservation field, one of the most sensitive points, since the options available do not offer reliable solutions. Most of the times, the product applied, specifically in earth heritage, do not embrace two of the most important aspects in any conservation procedure: compatibility and reversibility. This paper aims to review the main consolidants (natural and synthetic) commonly used in earth heritage conservation, and also to draw the attention for the importance of a solid diagnosis of the initial state of conservation. With this review, it was possible to understand a lack of homogeneity in the identification of decay phenomena, as well as in recognizing its mechanisms of occurrence, and consequently in choosing the proper consolidant or treatment.