Abstract: Embodiments provide methods for the protection and consolidation of calcareous materials. An exemplary method includes providing an aqueous solution of a hydroxycarboxylic acid, adjusting the pH of the aqueous solution by adding an alkaline agent, and applying the pH-adjusted aqueous solution to a calcareous mineral to form a conversion layer on the mineral. The calcareous mineral may, for example, be carbonate rock, particularly limestone and marble, or may be part of masonry material, aggregates, or fillers. Adherent conversion layers are readily formed at ambient temperatures and, therefore, methods provided are suitable for field application. Conversion layers so formed are provided as further embodiments.