After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone (conditioning of the materials prior to shaping C04B40/00; applying liquids or other fluent materials to surfaces, in general B05; grinding or polishing B24; apparatus or processes for treating or working shaped articles of clay or other ceramic compositions, slag or mixtures containing cementitious material B28B11/00; working stone or stone-like materials B28D; glazes, other than cold glazes, C03C8/00; etching, surface-brightening or pickling compositions C09K13/00)