During the recent restoration of the Ottoman part of the Császár Bath in Budapest, dated back to the 16th century, brick-lime plasters and mortars of different colours (white, pink, and red) were identified in the interior. Archaeometric study of brick-lime plasters and mortars aimed at determining their composition, hydraulic properties as well as to reveal the preparation technology. In the brick-lime mixtures, commonly used in the Ottoman times for several water-resistant building constructions (e.g. baths), brick fragments and brick dust play a role as pozzolanas (latent hydraulic aggregates) in the formation of the hydraulic character of mortars and plasters. Preliminary results indicate that the lime used for producing mortars and plasters also had hydraulic properties. The high Si content of the limy matrix, zoned “lime lumps” containing high amount of Si, silicate grains with Ca-rich diffusion rims and the card-house microstructure of the matrix suggest that the lime was produced by calcination of impure limestone (i.e. limestone with silicate impurities).