Before or after drilling the bore holes, chip off the damaged plaster for a minimum of 80 cm beyond the visible damp and salt area. Chemical injection is not suitable for gypseous brickwork. Therefore, gypseous mortar or plaster must be completely removed. If necessary, clean the brickwork mechanically. Pressureless injection: Pressureless injection is particularly suited for slightly damp or damp brickwork. Drill holes for the silicification fluid with a diameter of 30 mm, an average of approx. 12 cm apart and a slope of at least 30° (not more than 45°). Pressure injection: Pressure injection is especially suited for saturated substrates. Drill holes of 12 to 18 mm diameter (depending on the type and size of injection tube used), an average distance of approx. 12 cm and a slope of approx. 30°. At a slope of 30°, the depth of the bore holes should be equivalent to the thick- ness of the brickwork to ensure that 5 cm of the walls to be treated are not drilled through. Drill the holes in one or two rows. In the latter case, drill two staggered rows of holes on top of each other, with the holes approx. 8 cm apart. Use an electropneumatic drill or a core drill with as little vibration as possible. Position the holes so that at least one course joint is penetrated. Walls of more than 60 cm thickness and wall corners must be treated on both sides. Walls with larger cavities or cracks, and walls made of hollow blocks or loosely filled with mortar and stone in the core must be grouted with CR 65 sealing slurry (8 l of water on 25 kg) before injection of the silicification fluid. After the slurry has hardened, re-drill the holes. After drilling, blow the bore holes free of dust.