A sophisticated impregnation technique was designed in situ for a piece of rock. The stone was covered with several layers of different materials and specially sealed in the solidified soil. After the pressure within the piece of rock was lowered, the conservation and consolidation materials based on alkylalkoxysilanes and acrylic resins were introduced. The penetration of tuff in this particular case reached several centimeters and it was found that the rock was in good enough shape to be reused in a pool in a Japanese garden.