Many important buildings in Hungary, especially those built in the last 150 years, have been built of Sóskut, a porous limestone quarried in the Buda mountains. When exposed to climatic effects, mainly frost, and increasing atmospheric pollution, this stone deteriorates rapidly. After laboratory and field tests, trial cleanings have been carried out. Morphology changes have been tracked by scanning electron microscopy, and changes in the chemical composition of the weathered limestone layer by energy-dispersive x-ray analysis. Among the three cleaning technologies of water jet and other wet technologies, mechanical cleaning by wet sand blasting, and ion exchange absorption cleaning, the method that gave best results was found to be the last one. It removed as much dirt and weathering products as possible without detriment to the stone texture.