Ornamental rocks coloring without use of pigments comprises dipping in reducing agent for filtraiton, under specific controlled conditions

摘要

Ornamental rocks coloring without the use of pigments comprises e.g. dipping of the sheets of rock in a solution of a strong reducing agent whose pH and redox potential is controlled automatically by additives. An independent claim is included for an apparatus for the above process. The apparatus has a closed agitated vessel, and settled salts and rock fragments filtration is supplemented by process parameters meters with electrically-controlled addition feed valves.